/ library-functions.html

# Built-in Functions

The Python interpreter has a number of functions and types built into it that are always available. They are listed here in alphabetical order.

Built-in Functions

`abs()`

`delattr()`

`hash()`

`memoryview()`

`set()`

`all()`

`dict()`

`help()`

`min()`

`setattr()`

`any()`

`dir()`

`hex()`

`next()`

`slice()`

`ascii()`

`divmod()`

`id()`

`object()`

`sorted()`

`bin()`

`enumerate()`

`input()`

`oct()`

`staticmethod()`

`bool()`

`eval()`

`int()`

`open()`

`str()`

`breakpoint()`

`exec()`

`isinstance()`

`ord()`

`sum()`

`bytearray()`

`filter()`

`issubclass()`

`pow()`

`super()`

`bytes()`

`float()`

`iter()`

`print()`

`tuple()`

`callable()`

`format()`

`len()`

`property()`

`type()`

`chr()`

`frozenset()`

`list()`

`range()`

`vars()`

`classmethod()`

`getattr()`

`locals()`

`repr()`

`zip()`

`compile()`

`globals()`

`map()`

`reversed()`

`__import__()`

`complex()`

`hasattr()`

`max()`

`round()`

`abs` ( x )

Return the absolute value of a number. The argument may be an integer or a floating point number. If the argument is a complex number, its magnitude is returned. If x defines `__abs__()`, `abs(x)` returns `x.__abs__()`.

`all` ( iterable )

Return `True` if all elements of the iterable are true (or if the iterable is empty). Equivalent to:

``````def all(iterable):
for element in iterable:
if not element:
return False
return True
``````
`any` ( iterable )

Return `True` if any element of the iterable is true. If the iterable is empty, return `False`. Equivalent to:

``````def any(iterable):
for element in iterable:
if element:
return True
return False
``````
`ascii` ( object )

As `repr()`, return a string containing a printable representation of an object, but escape the non-ASCII characters in the string returned by `repr()` using `\x`, `\u` or `\U` escapes. This generates a string similar to that returned by `repr()` in Python 2.

`bin` ( x )

Convert an integer number to a binary string prefixed with “0b”. The result is a valid Python expression. If x is not a Python `int` object, it has to define an `__index__()` method that returns an integer. Some examples:

``````>>> bin(3)
'0b11'
>>> bin(-10)
'-0b1010'
``````

If prefix “0b” is desired or not, you can use either of the following ways.

``````>>> format(14, '#b'), format(14, 'b')
('0b1110', '1110')
>>> f'{14:#b}', f'{14:b}'
('0b1110', '1110')
``````

See also `format()` for more information.

class `bool` ( [ x ] )

Return a Boolean value, i.e. one of `True` or `False`. x is converted using the standard truth testing procedure. If x is false or omitted, this returns `False`; otherwise it returns `True`. The `bool` class is a subclass of `int` (see Numeric Types — int, float, complex). It cannot be subclassed further. Its only instances are `False` and `True` (see Boolean Values).

Changed in version 3.7: x is now a positional-only parameter.

`breakpoint` ( *args, **kws )

This function drops you into the debugger at the call site. Specifically, it calls `sys.breakpointhook()`, passing `args` and `kws` straight through. By default, `sys.breakpointhook()` calls `pdb.set_trace()` expecting no arguments. In this case, it is purely a convenience function so you don’t have to explicitly import `pdb` or type as much code to enter the debugger. However, `sys.breakpointhook()` can be set to some other function and `breakpoint()` will automatically call that, allowing you to drop into the debugger of choice.

Raises an auditing event `builtins.breakpoint` with argument `breakpointhook`.

New in version 3.7.

class `bytearray` ( [ source [, encoding [, errors ] ] ] )

Return a new array of bytes. The `bytearray` class is a mutable sequence of integers in the range 0 <= x < 256. It has most of the usual methods of mutable sequences, described in Mutable Sequence Types, as well as most methods that the `bytes` type has, see Bytes and Bytearray Operations.

The optional source parameter can be used to initialize the array in a few different ways:

• If it is a string, you must also give the encoding (and optionally, errors) parameters; `bytearray()` then converts the string to bytes using `str.encode()`.

• If it is an integer, the array will have that size and will be initialized with null bytes.

• If it is an object conforming to the buffer interface, a read-only buffer of the object will be used to initialize the bytes array.

• If it is an iterable, it must be an iterable of integers in the range `0 <= x < 256`, which are used as the initial contents of the array.

Without an argument, an array of size 0 is created.

class `bytes` ( [ source [, encoding [, errors ] ] ] )

Return a new “bytes” object, which is an immutable sequence of integers in the range `0 <= x < 256`. `bytes` is an immutable version of `bytearray` – it has the same non-mutating methods and the same indexing and slicing behavior.

Accordingly, constructor arguments are interpreted as for `bytearray()`.

Bytes objects can also be created with literals, see String and Bytes literals.

`callable` ( object )

Return `True` if the object argument appears callable, `False` if not. If this returns `True`, it is still possible that a call fails, but if it is `False`, calling object will never succeed. Note that classes are callable (calling a class returns a new instance); instances are callable if their class has a `__call__()` method.

New in version 3.2: This function was first removed in Python 3.0 and then brought back in Python 3.2.

`chr` ( i )

Return the string representing a character whose Unicode code point is the integer i. For example, `chr(97)` returns the string `'a'`, while `chr(8364)` returns the string `'€'`. This is the inverse of `ord()`.

The valid range for the argument is from 0 through 1,114,111 (0x10FFFF in base 16). `ValueError` will be raised if i is outside that range.

`@` `classmethod`

Transform a method into a class method.

A class method receives the class as implicit first argument, just like an instance method receives the instance. To declare a class method, use this idiom:

``````class C:
@classmethod
def f(cls, arg1, arg2, ...): ...
``````

The `@classmethod` form is a function decorator – see Function definitions for details.

A class method can be called either on the class (such as `C.f()`) or on an instance (such as `C().f()`). The instance is ignored except for its class. If a class method is called for a derived class, the derived class object is passed as the implied first argument.

Class methods are different than C++ or Java static methods. If you want those, see `staticmethod()`.

`compile` ( source, filename, mode, flags=0, dont_inherit=False, optimize=-1 )

Compile the source into a code or AST object. Code objects can be executed by `exec()` or `eval()`. source can either be a normal string, a byte string, or an AST object. Refer to the `ast` module documentation for information on how to work with AST objects.

The filename argument should give the file from which the code was read; pass some recognizable value if it wasn’t read from a file (`'<string>'` is commonly used).

The mode argument specifies what kind of code must be compiled; it can be `'exec'` if source consists of a sequence of statements, `'eval'` if it consists of a single expression, or `'single'` if it consists of a single interactive statement (in the latter case, expression statements that evaluate to something other than `None` will be printed).

The optional arguments flags and dont_inherit control which future statements affect the compilation of source. If neither is present (or both are zero) the code is compiled with those future statements that are in effect in the code that is calling `compile()`. If the flags argument is given and dont_inherit is not (or is zero) then the future statements specified by the flags argument are used in addition to those that would be used anyway. If dont_inherit is a non-zero integer then the flags argument is it – the future statements in effect around the call to compile are ignored.

Future statements are specified by bits which can be bitwise ORed together to specify multiple statements. The bitfield required to specify a given feature can be found as the `compiler_flag` attribute on the `_Feature` instance in the `__future__` module.

The optional argument flags also controls whether the compiled source is allowed to contain top-level `await`, `async for` and `async with`. When the bit `ast.PyCF_ALLOW_TOP_LEVEL_AWAIT` is set, the return code object has `CO_COROUTINE` set in `co_code`, and can be interactively executed via `await eval(code_object)`.

The argument optimize specifies the optimization level of the compiler; the default value of `-1` selects the optimization level of the interpreter as given by `-O` options. Explicit levels are `0` (no optimization; `__debug__` is true), `1` (asserts are removed, `__debug__` is false) or `2` (docstrings are removed too).

This function raises `SyntaxError` if the compiled source is invalid, and `ValueError` if the source contains null bytes.

If you want to parse Python code into its AST representation, see `ast.parse()`.

Raises an auditing event `compile` with arguments `source` and `filename`. This event may also be raised by implicit compilation.

Note

When compiling a string with multi-line code in `'single'` or `'eval'` mode, input must be terminated by at least one newline character. This is to facilitate detection of incomplete and complete statements in the `code` module.

Warning

It is possible to crash the Python interpreter with a sufficiently large/complex string when compiling to an AST object due to stack depth limitations in Python’s AST compiler.

Changed in version 3.2: Allowed use of Windows and Mac newlines. Also input in `'exec'` mode does not have to end in a newline anymore. Added the optimize parameter.

Changed in version 3.5: Previously, `TypeError` was raised when null bytes were encountered in source.

New in version 3.8: `ast.PyCF_ALLOW_TOP_LEVEL_AWAIT` can now be passed in flags to enable support for top-level `await`, `async for`, and `async with`.

class `complex` ( [ real [, imag ] ] )

Return a complex number with the value real + imag*1j or convert a string or number to a complex number. If the first parameter is a string, it will be interpreted as a complex number and the function must be called without a second parameter. The second parameter can never be a string. Each argument may be any numeric type (including complex). If imag is omitted, it defaults to zero and the constructor serves as a numeric conversion like `int` and `float`. If both arguments are omitted, returns `0j`.

For a general Python object `x`, `complex(x)` delegates to `x.__complex__()`. If `__complex__()` is not defined then it falls back to `__float__()`. If `__float__()` is not defined then it falls back to `__index__()`.

Note

When converting from a string, the string must not contain whitespace around the central `+` or `-` operator. For example, `complex('1+2j')` is fine, but `complex('1 + 2j')` raises `ValueError`.

The complex type is described in Numeric Types — int, float, complex.

Changed in version 3.6: Grouping digits with underscores as in code literals is allowed.

Changed in version 3.8: Falls back to `__index__()` if `__complex__()` and `__float__()` are not defined.

`delattr` ( object, name )

This is a relative of `setattr()`. The arguments are an object and a string. The string must be the name of one of the object’s attributes. The function deletes the named attribute, provided the object allows it. For example, `delattr(x, 'foobar')` is equivalent to `del x.foobar`.

class `dict` ( **kwarg )
class `dict` ( mapping, **kwarg )
class `dict` ( iterable, **kwarg )

Create a new dictionary. The `dict` object is the dictionary class. See `dict` and Mapping Types — dict for documentation about this class.

For other containers see the built-in `list`, `set`, and `tuple` classes, as well as the `collections` module.

`dir` ( [ object ] )

Without arguments, return the list of names in the current local scope. With an argument, attempt to return a list of valid attributes for that object.

If the object has a method named `__dir__()`, this method will be called and must return the list of attributes. This allows objects that implement a custom `__getattr__()` or `__getattribute__()` function to customize the way `dir()` reports their attributes.

If the object does not provide `__dir__()`, the function tries its best to gather information from the object’s `__dict__` attribute, if defined, and from its type object. The resulting list is not necessarily complete, and may be inaccurate when the object has a custom `__getattr__()`.

The default `dir()` mechanism behaves differently with different types of objects, as it attempts to produce the most relevant, rather than complete, information:

• If the object is a module object, the list contains the names of the module’s attributes.

• If the object is a type or class object, the list contains the names of its attributes, and recursively of the attributes of its bases.

• Otherwise, the list contains the object’s attributes’ names, the names of its class’s attributes, and recursively of the attributes of its class’s base classes.

The resulting list is sorted alphabetically. For example:

``````>>> import struct
>>> dir()   # show the names in the module namespace
['__builtins__', '__name__', 'struct']
>>> dir(struct)   # show the names in the struct module
['Struct', '__all__', '__builtins__', '__cached__', '__doc__', '__file__',
'_clearcache', 'calcsize', 'error', 'pack', 'pack_into',
'unpack', 'unpack_from']
>>> class Shape:
...     def __dir__(self):
...         return ['area', 'perimeter', 'location']
>>> s = Shape()
>>> dir(s)
['area', 'location', 'perimeter']
``````

Note

Because `dir()` is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names, and its detailed behavior may change across releases. For example, metaclass attributes are not in the result list when the argument is a class.

`divmod` ( a, b )

Take two (non complex) numbers as arguments and return a pair of numbers consisting of their quotient and remainder when using integer division. With mixed operand types, the rules for binary arithmetic operators apply. For integers, the result is the same as `(a // b, a % b)`. For floating point numbers the result is `(q, a % b)`, where q is usually `math.floor(a / b)` but may be 1 less than that. In any case `q * b + a % b` is very close to a, if `a % b` is non-zero it has the same sign as b, and `0 <= abs(a % b) < abs(b)`.

`enumerate` ( iterable, start=0 )

Return an enumerate object. iterable must be a sequence, an iterator, or some other object which supports iteration. The `__next__()` method of the iterator returned by `enumerate()` returns a tuple containing a count (from start which defaults to 0) and the values obtained from iterating over iterable.

``````>>> seasons = ['Spring', 'Summer', 'Fall', 'Winter']
>>> list(enumerate(seasons))
[(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]
>>> list(enumerate(seasons, start=1))
[(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]
``````

Equivalent to:

``````def enumerate(sequence, start=0):
n = start
for elem in sequence:
yield n, elem
n += 1
``````
`eval` ( expression [, globals [, locals ] ] )

The arguments are a string and optional globals and locals. If provided, globals must be a dictionary. If provided, locals can be any mapping object.

The expression argument is parsed and evaluated as a Python expression (technically speaking, a condition list) using the globals and locals dictionaries as global and local namespace. If the globals dictionary is present and does not contain a value for the key `__builtins__`, a reference to the dictionary of the built-in module `builtins` is inserted under that key before expression is parsed. This means that expression normally has full access to the standard `builtins` module and restricted environments are propagated. If the locals dictionary is omitted it defaults to the globals dictionary. If both dictionaries are omitted, the expression is executed with the globals and locals in the environment where `eval()` is called. Note, eval() does not have access to the nested scopes (non-locals) in the enclosing environment.

The return value is the result of the evaluated expression. Syntax errors are reported as exceptions. Example:

``````>>> x = 1
>>> eval('x+1')
2
``````

This function can also be used to execute arbitrary code objects (such as those created by `compile()`). In this case pass a code object instead of a string. If the code object has been compiled with `'exec'` as the mode argument, `eval()`’s return value will be `None`.

Hints: dynamic execution of statements is supported by the `exec()` function. The `globals()` and `locals()` functions returns the current global and local dictionary, respectively, which may be useful to pass around for use by `eval()` or `exec()`.

See `ast.literal_eval()` for a function that can safely evaluate strings with expressions containing only literals.

Raises an auditing event `exec` with the code object as the argument. Code compilation events may also be raised.

`exec` ( object [, globals [, locals ] ] )

This function supports dynamic execution of Python code. object must be either a string or a code object. If it is a string, the string is parsed as a suite of Python statements which is then executed (unless a syntax error occurs). 1 If it is a code object, it is simply executed. In all cases, the code that’s executed is expected to be valid as file input (see the section “File input” in the Reference Manual). Be aware that the `return` and `yield` statements may not be used outside of function definitions even within the context of code passed to the `exec()` function. The return value is `None`.

In all cases, if the optional parts are omitted, the code is executed in the current scope. If only globals is provided, it must be a dictionary (and not a subclass of dictionary), which will be used for both the global and the local variables. If globals and locals are given, they are used for the global and local variables, respectively. If provided, locals can be any mapping object. Remember that at module level, globals and locals are the same dictionary. If exec gets two separate objects as globals and locals, the code will be executed as if it were embedded in a class definition.

If the globals dictionary does not contain a value for the key `__builtins__`, a reference to the dictionary of the built-in module `builtins` is inserted under that key. That way you can control what builtins are available to the executed code by inserting your own `__builtins__` dictionary into globals before passing it to `exec()`.

Raises an auditing event `exec` with the code object as the argument. Code compilation events may also be raised.

Note

The built-in functions `globals()` and `locals()` return the current global and local dictionary, respectively, which may be useful to pass around for use as the second and third argument to `exec()`.

Note

The default locals act as described for function `locals()` below: modifications to the default locals dictionary should not be attempted. Pass an explicit locals dictionary if you need to see effects of the code on locals after function `exec()` returns.

`filter` ( function, iterable )

Construct an iterator from those elements of iterable for which function returns true. iterable may be either a sequence, a container which supports iteration, or an iterator. If function is `None`, the identity function is assumed, that is, all elements of iterable that are false are removed.

Note that `filter(function, iterable)` is equivalent to the generator expression `(item for item in iterable if function(item))` if function is not `None` and `(item for item in iterable if item)` if function is `None`.

See `itertools.filterfalse()` for the complementary function that returns elements of iterable for which function returns false.

class `float` ( [ x ] )

Return a floating point number constructed from a number or string x.

If the argument is a string, it should contain a decimal number, optionally preceded by a sign, and optionally embedded in whitespace. The optional sign may be `'+'` or `'-'`; a `'+'` sign has no effect on the value produced. The argument may also be a string representing a NaN (not-a-number), or a positive or negative infinity. More precisely, the input must conform to the following grammar after leading and trailing whitespace characters are removed:

```sign           ::=  "+" | "-"
infinity       ::=  "Infinity" | "inf"
nan            ::=  "nan"
numeric_value  ::=  `floatnumber` | `infinity` | `nan`
numeric_string ::=  [`sign`] `numeric_value`
```

Here `floatnumber` is the form of a Python floating-point literal, described in Floating point literals. Case is not significant, so, for example, “inf”, “Inf”, “INFINITY” and “iNfINity” are all acceptable spellings for positive infinity.

Otherwise, if the argument is an integer or a floating point number, a floating point number with the same value (within Python’s floating point precision) is returned. If the argument is outside the range of a Python float, an `OverflowError` will be raised.

For a general Python object `x`, `float(x)` delegates to `x.__float__()`. If `__float__()` is not defined then it falls back to `__index__()`.

If no argument is given, `0.0` is returned.

Examples:

``````>>> float('+1.23')
1.23
>>> float('   -12345\n')
-12345.0
>>> float('1e-003')
0.001
>>> float('+1E6')
1000000.0
>>> float('-Infinity')
-inf
``````

The float type is described in Numeric Types — int, float, complex.

Changed in version 3.6: Grouping digits with underscores as in code literals is allowed.

Changed in version 3.7: x is now a positional-only parameter.

Changed in version 3.8: Falls back to `__index__()` if `__float__()` is not defined.

`format` ( value [, format_spec ] )

Convert a value to a “formatted” representation, as controlled by format_spec. The interpretation of format_spec will depend on the type of the value argument, however there is a standard formatting syntax that is used by most built-in types: Format Specification Mini-Language.

The default format_spec is an empty string which usually gives the same effect as calling `str(value)`.

A call to `format(value, format_spec)` is translated to `type(value).__format__(value, format_spec)` which bypasses the instance dictionary when searching for the value’s `__format__()` method. A `TypeError` exception is raised if the method search reaches `object` and the format_spec is non-empty, or if either the format_spec or the return value are not strings.

Changed in version 3.4: `object().__format__(format_spec)` raises `TypeError` if format_spec is not an empty string.

class `frozenset` ( [ iterable ] )

Return a new `frozenset` object, optionally with elements taken from iterable. `frozenset` is a built-in class. See `frozenset` and Set Types — set, frozenset for documentation about this class.

For other containers see the built-in `set`, `list`, `tuple`, and `dict` classes, as well as the `collections` module.

`getattr` ( object, name [, default ] )

Return the value of the named attribute of object. name must be a string. If the string is the name of one of the object’s attributes, the result is the value of that attribute. For example, `getattr(x, 'foobar')` is equivalent to `x.foobar`. If the named attribute does not exist, default is returned if provided, otherwise `AttributeError` is raised.

`globals` ( )

Return a dictionary representing the current global symbol table. This is always the dictionary of the current module (inside a function or method, this is the module where it is defined, not the module from which it is called).

`hasattr` ( object, name )

The arguments are an object and a string. The result is `True` if the string is the name of one of the object’s attributes, `False` if not. (This is implemented by calling `getattr(object, name)` and seeing whether it raises an `AttributeError` or not.)

`hash` ( object )

Return the hash value of the object (if it has one). Hash values are integers. They are used to quickly compare dictionary keys during a dictionary lookup. Numeric values that compare equal have the same hash value (even if they are of different types, as is the case for 1 and 1.0).

Note

For objects with custom `__hash__()` methods, note that `hash()` truncates the return value based on the bit width of the host machine. See `__hash__()` for details.

`help` ( [ object ] )

Invoke the built-in help system. (This function is intended for interactive use.) If no argument is given, the interactive help system starts on the interpreter console. If the argument is a string, then the string is looked up as the name of a module, function, class, method, keyword, or documentation topic, and a help page is printed on the console. If the argument is any other kind of object, a help page on the object is generated.

Note that if a slash(/) appears in the parameter list of a function, when invoking `help()`, it means that the parameters prior to the slash are positional-only. For more info, see the FAQ entry on positional-only parameters.

This function is added to the built-in namespace by the `site` module.

Changed in version 3.4: Changes to `pydoc` and `inspect` mean that the reported signatures for callables are now more comprehensive and consistent.

`hex` ( x )

Convert an integer number to a lowercase hexadecimal string prefixed with “0x”. If x is not a Python `int` object, it has to define an `__index__()` method that returns an integer. Some examples:

``````>>> hex(255)
'0xff'
>>> hex(-42)
'-0x2a'
``````

If you want to convert an integer number to an uppercase or lower hexadecimal string with prefix or not, you can use either of the following ways:

``````>>> '%#x' % 255, '%x' % 255, '%X' % 255
('0xff', 'ff', 'FF')
>>> format(255, '#x'), format(255, 'x'), format(255, 'X')
('0xff', 'ff', 'FF')
>>> f'{255:#x}', f'{255:x}', f'{255:X}'
('0xff', 'ff', 'FF')
``````

See also `format()` for more information.

See also `int()` for converting a hexadecimal string to an integer using a base of 16.

Note

To obtain a hexadecimal string representation for a float, use the `float.hex()` method.

`id` ( object )

Return the “identity” of an object. This is an integer which is guaranteed to be unique and constant for this object during its lifetime. Two objects with non-overlapping lifetimes may have the same `id()` value.

CPython implementation detail: This is the address of the object in memory.

`input` ( [ prompt ] )

If the prompt argument is present, it is written to standard output without a trailing newline. The function then reads a line from input, converts it to a string (stripping a trailing newline), and returns that. When EOF is read, `EOFError` is raised. Example:

``````>>> s = input('--> ')
--> Monty Python's Flying Circus
>>> s
"Monty Python's Flying Circus"
``````

If the `readline` module was loaded, then `input()` will use it to provide elaborate line editing and history features.

Raises an auditing event `builtins.input` with argument `prompt` before reading input

Raises an auditing event `builtins.input/result` with the result after successfully reading input.

class `int` ( [ x ] )
class `int` ( x, base=10 )

Return an integer object constructed from a number or string x, or return `0` if no arguments are given. If x defines `__int__()`, `int(x)` returns `x.__int__()`. If x defines `__index__()`, it returns `x.__index__()`. If x defines `__trunc__()`, it returns `x.__trunc__()`. For floating point numbers, this truncates towards zero.

If x is not a number or if base is given, then x must be a string, `bytes`, or `bytearray` instance representing an integer literal in radix base. Optionally, the literal can be preceded by `+` or `-` (with no space in between) and surrounded by whitespace. A base-n literal consists of the digits 0 to n-1, with `a` to `z` (or `A` to `Z`) having values 10 to 35. The default base is 10. The allowed values are 0 and 2–36. Base-2, -8, and -16 literals can be optionally prefixed with `0b`/`0B`, `0o`/`0O`, or `0x`/`0X`, as with integer literals in code. Base 0 means to interpret exactly as a code literal, so that the actual base is 2, 8, 10, or 16, and so that `int('010', 0)` is not legal, while `int('010')` is, as well as `int('010', 8)`.

The integer type is described in Numeric Types — int, float, complex.

Changed in version 3.4: If base is not an instance of `int` and the base object has a `base.__index__` method, that method is called to obtain an integer for the base. Previous versions used `base.__int__` instead of `base.__index__`.

Changed in version 3.6: Grouping digits with underscores as in code literals is allowed.

Changed in version 3.7: x is now a positional-only parameter.

Changed in version 3.8: Falls back to `__index__()` if `__int__()` is not defined.

`isinstance` ( object, classinfo )

Return `True` if the object argument is an instance of the classinfo argument, or of a (direct, indirect or virtual) subclass thereof. If object is not an object of the given type, the function always returns `False`. If classinfo is a tuple of type objects (or recursively, other such tuples), return `True` if object is an instance of any of the types. If classinfo is not a type or tuple of types and such tuples, a `TypeError` exception is raised.

`issubclass` ( class, classinfo )

Return `True` if class is a subclass (direct, indirect or virtual) of classinfo. A class is considered a subclass of itself. classinfo may be a tuple of class objects, in which case every entry in classinfo will be checked. In any other case, a `TypeError` exception is raised.

`iter` ( object [, sentinel ] )

Return an iterator object. The first argument is interpreted very differently depending on the presence of the second argument. Without a second argument, object must be a collection object which supports the iteration protocol (the `__iter__()` method), or it must support the sequence protocol (the `__getitem__()` method with integer arguments starting at `0`). If it does not support either of those protocols, `TypeError` is raised. If the second argument, sentinel, is given, then object must be a callable object. The iterator created in this case will call object with no arguments for each call to its `__next__()` method; if the value returned is equal to sentinel, `StopIteration` will be raised, otherwise the value will be returned.

One useful application of the second form of `iter()` is to build a block-reader. For example, reading fixed-width blocks from a binary database file until the end of file is reached:

``````from functools import partial
with open('mydata.db', 'rb') as f:
for block in iter(partial(f.read, 64), b''):
process_block(block)
``````
`len` ( s )

Return the length (the number of items) of an object. The argument may be a sequence (such as a string, bytes, tuple, list, or range) or a collection (such as a dictionary, set, or frozen set).

class `list` ( [ iterable ] )

Rather than being a function, `list` is actually a mutable sequence type, as documented in Lists and Sequence Types — list, tuple, range.

`locals` ( )

Update and return a dictionary representing the current local symbol table. Free variables are returned by `locals()` when it is called in function blocks, but not in class blocks. Note that at the module level, `locals()` and `globals()` are the same dictionary.

Note

The contents of this dictionary should not be modified; changes may not affect the values of local and free variables used by the interpreter.

`map` ( function, iterable, ... )

Return an iterator that applies function to every item of iterable, yielding the results. If additional iterable arguments are passed, function must take that many arguments and is applied to the items from all iterables in parallel. With multiple iterables, the iterator stops when the shortest iterable is exhausted. For cases where the function inputs are already arranged into argument tuples, see `itertools.starmap()`.

`max` ( iterable, * [, key, default ] )
`max` ( arg1, arg2, *args [, key ] )

Return the largest item in an iterable or the largest of two or more arguments.

If one positional argument is provided, it should be an iterable. The largest item in the iterable is returned. If two or more positional arguments are provided, the largest of the positional arguments is returned.

There are two optional keyword-only arguments. The key argument specifies a one-argument ordering function like that used for `list.sort()`. The default argument specifies an object to return if the provided iterable is empty. If the iterable is empty and default is not provided, a `ValueError` is raised.

If multiple items are maximal, the function returns the first one encountered. This is consistent with other sort-stability preserving tools such as `sorted(iterable, key=keyfunc, reverse=True)[0]` and `heapq.nlargest(1, iterable, key=keyfunc)`.

New in version 3.4: The default keyword-only argument.

Changed in version 3.8: The key can be `None`.

class `memoryview` ( obj )

Return a “memory view” object created from the given argument. See Memory Views for more information.

`min` ( iterable, * [, key, default ] )
`min` ( arg1, arg2, *args [, key ] )

Return the smallest item in an iterable or the smallest of two or more arguments.

If one positional argument is provided, it should be an iterable. The smallest item in the iterable is returned. If two or more positional arguments are provided, the smallest of the positional arguments is returned.

There are two optional keyword-only arguments. The key argument specifies a one-argument ordering function like that used for `list.sort()`. The default argument specifies an object to return if the provided iterable is empty. If the iterable is empty and default is not provided, a `ValueError` is raised.

If multiple items are minimal, the function returns the first one encountered. This is consistent with other sort-stability preserving tools such as `sorted(iterable, key=keyfunc)[0]` and `heapq.nsmallest(1, iterable, key=keyfunc)`.

New in version 3.4: The default keyword-only argument.

Changed in version 3.8: The key can be `None`.

`next` ( iterator [, default ] )

Retrieve the next item from the iterator by calling its `__next__()` method. If default is given, it is returned if the iterator is exhausted, otherwise `StopIteration` is raised.

class `object`

Return a new featureless object. `object` is a base for all classes. It has the methods that are common to all instances of Python classes. This function does not accept any arguments.

Note

`object` does not have a `__dict__`, so you can’t assign arbitrary attributes to an instance of the `object` class.

`oct` ( x )

Convert an integer number to an octal string prefixed with “0o”. The result is a valid Python expression. If x is not a Python `int` object, it has to define an `__index__()` method that returns an integer. For example:

``````>>> oct(8)
'0o10'
>>> oct(-56)
'-0o70'
``````

If you want to convert an integer number to octal string either with prefix “0o” or not, you can use either of the following ways.

``````>>> '%#o' % 10, '%o' % 10
('0o12', '12')
>>> format(10, '#o'), format(10, 'o')
('0o12', '12')
>>> f'{10:#o}', f'{10:o}'
('0o12', '12')
``````

See also `format()` for more information.

`open` ( file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None )

Open file and return a corresponding file object. If the file cannot be opened, an `OSError` is raised.

file is a path-like object giving the pathname (absolute or relative to the current working directory) of the file to be opened or an integer file descriptor of the file to be wrapped. (If a file descriptor is given, it is closed when the returned I/O object is closed, unless closefd is set to `False`.)

mode is an optional string that specifies the mode in which the file is opened. It defaults to `'r'` which means open for reading in text mode. Other common values are `'w'` for writing (truncating the file if it already exists), `'x'` for exclusive creation and `'a'` for appending (which on some Unix systems, means that all writes append to the end of the file regardless of the current seek position). In text mode, if encoding is not specified the encoding used is platform dependent: `locale.getpreferredencoding(False)` is called to get the current locale encoding. (For reading and writing raw bytes use binary mode and leave encoding unspecified.) The available modes are:

Character

Meaning

`'r'`

`'w'`

open for writing, truncating the file first

`'x'`

open for exclusive creation, failing if the file already exists

`'a'`

open for writing, appending to the end of the file if it exists

`'b'`

binary mode

`'t'`

text mode (default)

`'+'`

open for updating (reading and writing)

The default mode is `'r'` (open for reading text, synonym of `'rt'`). Modes `'w+'` and `'w+b'` open and truncate the file. Modes `'r+'` and `'r+b'` open the file with no truncation.

As mentioned in the Overview, Python distinguishes between binary and text I/O. Files opened in binary mode (including `'b'` in the mode argument) return contents as `bytes` objects without any decoding. In text mode (the default, or when `'t'` is included in the mode argument), the contents of the file are returned as `str`, the bytes having been first decoded using a platform-dependent encoding or using the specified encoding if given.

There is an additional mode character permitted, `'U'`, which no longer has any effect, and is considered deprecated. It previously enabled universal newlines in text mode, which became the default behaviour in Python 3.0. Refer to the documentation of the newline parameter for further details.

Note

Python doesn’t depend on the underlying operating system’s notion of text files; all the processing is done by Python itself, and is therefore platform-independent.

buffering is an optional integer used to set the buffering policy. Pass 0 to switch buffering off (only allowed in binary mode), 1 to select line buffering (only usable in text mode), and an integer > 1 to indicate the size in bytes of a fixed-size chunk buffer. When no buffering argument is given, the default buffering policy works as follows:

• Binary files are buffered in fixed-size chunks; the size of the buffer is chosen using a heuristic trying to determine the underlying device’s “block size” and falling back on `io.DEFAULT_BUFFER_SIZE`. On many systems, the buffer will typically be 4096 or 8192 bytes long.

• “Interactive” text files (files for which `isatty()` returns `True`) use line buffering. Other text files use the policy described above for binary files.

encoding is the name of the encoding used to decode or encode the file. This should only be used in text mode. The default encoding is platform dependent (whatever `locale.getpreferredencoding()` returns), but any text encoding supported by Python can be used. See the `codecs` module for the list of supported encodings.

errors is an optional string that specifies how encoding and decoding errors are to be handled—this cannot be used in binary mode. A variety of standard error handlers are available (listed under Error Handlers), though any error handling name that has been registered with `codecs.register_error()` is also valid. The standard names include:

• `'strict'` to raise a `ValueError` exception if there is an encoding error. The default value of `None` has the same effect.

• `'ignore'` ignores errors. Note that ignoring encoding errors can lead to data loss.

• `'replace'` causes a replacement marker (such as `'?'`) to be inserted where there is malformed data.

• `'surrogateescape'` will represent any incorrect bytes as code points in the Unicode Private Use Area ranging from U+DC80 to U+DCFF. These private code points will then be turned back into the same bytes when the `surrogateescape` error handler is used when writing data. This is useful for processing files in an unknown encoding.

• `'xmlcharrefreplace'` is only supported when writing to a file. Characters not supported by the encoding are replaced with the appropriate XML character reference `&#nnn;`.

• `'backslashreplace'` replaces malformed data by Python’s backslashed escape sequences.

• `'namereplace'` (also only supported when writing) replaces unsupported characters with `\N{...}` escape sequences.

newline controls how universal newlines mode works (it only applies to text mode). It can be `None`, `''`, `'\n'`, `'\r'`, and `'\r\n'`. It works as follows:

• When reading input from the stream, if newline is `None`, universal newlines mode is enabled. Lines in the input can end in `'\n'`, `'\r'`, or `'\r\n'`, and these are translated into `'\n'` before being returned to the caller. If it is `''`, universal newlines mode is enabled, but line endings are returned to the caller untranslated. If it has any of the other legal values, input lines are only terminated by the given string, and the line ending is returned to the caller untranslated.

• When writing output to the stream, if newline is `None`, any `'\n'` characters written are translated to the system default line separator, `os.linesep`. If newline is `''` or `'\n'`, no translation takes place. If newline is any of the other legal values, any `'\n'` characters written are translated to the given string.

If closefd is `False` and a file descriptor rather than a filename was given, the underlying file descriptor will be kept open when the file is closed. If a filename is given closefd must be `True` (the default) otherwise an error will be raised.

A custom opener can be used by passing a callable as opener. The underlying file descriptor for the file object is then obtained by calling opener with (file, flags). opener must return an open file descriptor (passing `os.open` as opener results in functionality similar to passing `None`).

The newly created file is non-inheritable.

The following example uses the dir_fd parameter of the `os.open()` function to open a file relative to a given directory:

``````>>> import os
>>> dir_fd = os.open('somedir', os.O_RDONLY)
>>> def opener(path, flags):
...     return os.open(path, flags, dir_fd=dir_fd)
...
>>> with open('spamspam.txt', 'w', opener=opener) as f:
...     print('This will be written to somedir/spamspam.txt', file=f)
...
>>> os.close(dir_fd)  # don't leak a file descriptor
``````

The type of file object returned by the `open()` function depends on the mode. When `open()` is used to open a file in a text mode (`'w'`, `'r'`, `'wt'`, `'rt'`, etc.), it returns a subclass of `io.TextIOBase` (specifically `io.TextIOWrapper`). When used to open a file in a binary mode with buffering, the returned class is a subclass of `io.BufferedIOBase`. The exact class varies: in read binary mode, it returns an `io.BufferedReader`; in write binary and append binary modes, it returns an `io.BufferedWriter`, and in read/write mode, it returns an `io.BufferedRandom`. When buffering is disabled, the raw stream, a subclass of `io.RawIOBase`, `io.FileIO`, is returned.

See also the file handling modules, such as, `fileinput`, `io` (where `open()` is declared), `os`, `os.path`, `tempfile`, and `shutil`.

Raises an auditing event `open` with arguments `file`, `mode`, `flags`.

The `mode` and `flags` arguments may have been modified or inferred from the original call.

Changed in version 3.3:
Changed in version 3.4:
• The file is now non-inheritable.

Deprecated since version 3.4, will be removed in version 3.9: The `'U'` mode.

Changed in version 3.5:
• If the system call is interrupted and the signal handler does not raise an exception, the function now retries the system call instead of raising an `InterruptedError` exception (see PEP 475 for the rationale).

• The `'namereplace'` error handler was added.

Changed in version 3.6:
`ord` ( c )

Given a string representing one Unicode character, return an integer representing the Unicode code point of that character. For example, `ord('a')` returns the integer `97` and `ord('€')` (Euro sign) returns `8364`. This is the inverse of `chr()`.

`pow` ( base, exp [, mod ] )

Return base to the power exp; if mod is present, return base to the power exp, modulo mod (computed more efficiently than `pow(base, exp) % mod`). The two-argument form `pow(base, exp)` is equivalent to using the power operator: `base**exp`.

The arguments must have numeric types. With mixed operand types, the coercion rules for binary arithmetic operators apply. For `int` operands, the result has the same type as the operands (after coercion) unless the second argument is negative; in that case, all arguments are converted to float and a float result is delivered. For example, `10**2` returns `100`, but `10**-2` returns `0.01`.

For `int` operands base and exp, if mod is present, mod must also be of integer type and mod must be nonzero. If mod is present and exp is negative, base must be relatively prime to mod. In that case, `pow(inv_base, -exp, mod)` is returned, where inv_base is an inverse to base modulo mod.

Here’s an example of computing an inverse for `38` modulo `97`:

``````>>> pow(38, -1, mod=97)
23
>>> 23 * 38 % 97 == 1
True
``````

Changed in version 3.8: For `int` operands, the three-argument form of `pow` now allows the second argument to be negative, permitting computation of modular inverses.

Changed in version 3.8: Allow keyword arguments. Formerly, only positional arguments were supported.

`print` ( *objects, sep=' ', end='\n', file=sys.stdout, flush=False )

Print objects to the text stream file, separated by sep and followed by end. sep, end, file and flush, if present, must be given as keyword arguments.

All non-keyword arguments are converted to strings like `str()` does and written to the stream, separated by sep and followed by end. Both sep and end must be strings; they can also be `None`, which means to use the default values. If no objects are given, `print()` will just write end.

The file argument must be an object with a `write(string)` method; if it is not present or `None`, `sys.stdout` will be used. Since printed arguments are converted to text strings, `print()` cannot be used with binary mode file objects. For these, use `file.write(...)` instead.

Whether output is buffered is usually determined by file, but if the flush keyword argument is true, the stream is forcibly flushed.

Changed in version 3.3: Added the flush keyword argument.

class `property` ( fget=None, fset=None, fdel=None, doc=None )

Return a property attribute.

fget is a function for getting an attribute value. fset is a function for setting an attribute value. fdel is a function for deleting an attribute value. And doc creates a docstring for the attribute.

A typical use is to define a managed attribute `x`:

``````class C:
def __init__(self):
self._x = None

def getx(self):
return self._x

def setx(self, value):
self._x = value

def delx(self):
del self._x

x = property(getx, setx, delx, "I'm the 'x' property.")
``````

If c is an instance of C, `c.x` will invoke the getter, `c.x = value` will invoke the setter and `del c.x` the deleter.

If given, doc will be the docstring of the property attribute. Otherwise, the property will copy fget’s docstring (if it exists). This makes it possible to create read-only properties easily using `property()` as a decorator:

``````class Parrot:
def __init__(self):
self._voltage = 100000

@property
def voltage(self):
"""Get the current voltage."""
return self._voltage
``````

The `@property` decorator turns the `voltage()` method into a “getter” for a read-only attribute with the same name, and it sets the docstring for voltage to “Get the current voltage.”

A property object has `getter`, `setter`, and `deleter` methods usable as decorators that create a copy of the property with the corresponding accessor function set to the decorated function. This is best explained with an example:

``````class C:
def __init__(self):
self._x = None

@property
def x(self):
"""I'm the 'x' property."""
return self._x

@x.setter
def x(self, value):
self._x = value

@x.deleter
def x(self):
del self._x
``````

This code is exactly equivalent to the first example. Be sure to give the additional functions the same name as the original property (`x` in this case.)

The returned property object also has the attributes `fget`, `fset`, and `fdel` corresponding to the constructor arguments.

Changed in version 3.5: The docstrings of property objects are now writeable.

class `range` ( stop )
class `range` ( start, stop [, step ] )

Rather than being a function, `range` is actually an immutable sequence type, as documented in Ranges and Sequence Types — list, tuple, range.

`repr` ( object )

Return a string containing a printable representation of an object. For many types, this function makes an attempt to return a string that would yield an object with the same value when passed to `eval()`, otherwise the representation is a string enclosed in angle brackets that contains the name of the type of the object together with additional information often including the name and address of the object. A class can control what this function returns for its instances by defining a `__repr__()` method.

`reversed` ( seq )

Return a reverse iterator. seq must be an object which has a `__reversed__()` method or supports the sequence protocol (the `__len__()` method and the `__getitem__()` method with integer arguments starting at `0`).

`round` ( number [, ndigits ] )

Return number rounded to ndigits precision after the decimal point. If ndigits is omitted or is `None`, it returns the nearest integer to its input.

For the built-in types supporting `round()`, values are rounded to the closest multiple of 10 to the power minus ndigits; if two multiples are equally close, rounding is done toward the even choice (so, for example, both `round(0.5)` and `round(-0.5)` are `0`, and `round(1.5)` is `2`). Any integer value is valid for ndigits (positive, zero, or negative). The return value is an integer if ndigits is omitted or `None`. Otherwise the return value has the same type as number.

For a general Python object `number`, `round` delegates to `number.__round__`.

Note

The behavior of `round()` for floats can be surprising: for example, `round(2.675, 2)` gives `2.67` instead of the expected `2.68`. This is not a bug: it’s a result of the fact that most decimal fractions can’t be represented exactly as a float. See Floating Point Arithmetic: Issues and Limitations for more information.

class `set` ( [ iterable ] )

Return a new `set` object, optionally with elements taken from iterable. `set` is a built-in class. See `set` and Set Types — set, frozenset for documentation about this class.

For other containers see the built-in `frozenset`, `list`, `tuple`, and `dict` classes, as well as the `collections` module.

`setattr` ( object, name, value )

This is the counterpart of `getattr()`. The arguments are an object, a string and an arbitrary value. The string may name an existing attribute or a new attribute. The function assigns the value to the attribute, provided the object allows it. For example, `setattr(x, 'foobar', 123)` is equivalent to `x.foobar = 123`.

class `slice` ( stop )
class `slice` ( start, stop [, step ] )

Return a slice object representing the set of indices specified by `range(start, stop, step)`. The start and step arguments default to `None`. Slice objects have read-only data attributes `start`, `stop` and `step` which merely return the argument values (or their default). They have no other explicit functionality; however they are used by Numerical Python and other third party extensions. Slice objects are also generated when extended indexing syntax is used. For example: `a[start:stop:step]` or `a[start:stop, i]`. See `itertools.islice()` for an alternate version that returns an iterator.

`sorted` ( iterable, *, key=None, reverse=False )

Return a new sorted list from the items in iterable.

Has two optional arguments which must be specified as keyword arguments.

key specifies a function of one argument that is used to extract a comparison key from each element in iterable (for example, `key=str.lower`). The default value is `None` (compare the elements directly).

reverse is a boolean value. If set to `True`, then the list elements are sorted as if each comparison were reversed.

Use `functools.cmp_to_key()` to convert an old-style cmp function to a key function.

The built-in `sorted()` function is guaranteed to be stable. A sort is stable if it guarantees not to change the relative order of elements that compare equal — this is helpful for sorting in multiple passes (for example, sort by department, then by salary grade).

For sorting examples and a brief sorting tutorial, see Sorting HOW TO.

`@` `staticmethod`

Transform a method into a static method.

A static method does not receive an implicit first argument. To declare a static method, use this idiom:

``````class C:
@staticmethod
def f(arg1, arg2, ...): ...
``````

The `@staticmethod` form is a function decorator – see Function definitions for details.

A static method can be called either on the class (such as `C.f()`) or on an instance (such as `C().f()`).

Static methods in Python are similar to those found in Java or C++. Also see `classmethod()` for a variant that is useful for creating alternate class constructors.

Like all decorators, it is also possible to call `staticmethod` as a regular function and do something with its result. This is needed in some cases where you need a reference to a function from a class body and you want to avoid the automatic transformation to instance method. For these cases, use this idiom:

``````class C:
builtin_open = staticmethod(open)
``````

class `str` ( object='' )
class `str` ( object=b'', encoding='utf-8', errors='strict' )
Return a `str` version of object. See `str()` for details.
`str` is the built-in string class. For general information about strings, see Text Sequence Type — str.
`sum` ( iterable, /, start=0 )