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7.1. string — Common string operations
Source code: Lib/string.py
The string
module contains a number of useful constants and classes, as well as some deprecated legacy functions that are also available as methods on strings. In addition, Python’s built-in string classes support the sequence type methods described in the Sequence Types — str, unicode, list, tuple, bytearray, buffer, xrange section, and also the string-specific methods described in the String Methods section. To output formatted strings use template strings or the %
operator described in the String Formatting Operations section. Also, see the re
module for string functions based on regular expressions.
7.1.1. String constants
The constants defined in this module are:
string.
ascii_letters
-
The concatenation of the
ascii_lowercase
andascii_uppercase
constants described below. This value is not locale-dependent.
string.
ascii_lowercase
-
The lowercase letters
'abcdefghijklmnopqrstuvwxyz'
. This value is not locale-dependent and will not change.
string.
ascii_uppercase
-
The uppercase letters
'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
. This value is not locale-dependent and will not change.
string.
letters
-
The concatenation of the strings
lowercase
anduppercase
described below. The specific value is locale-dependent, and will be updated whenlocale.setlocale()
is called.
string.
lowercase
-
A string containing all the characters that are considered lowercase letters. On most systems this is the string
'abcdefghijklmnopqrstuvwxyz'
. The specific value is locale-dependent, and will be updated whenlocale.setlocale()
is called.
string.
punctuation
-
String of ASCII characters which are considered punctuation characters in the
C
locale.
string.
printable
-
String of characters which are considered printable. This is a combination of
digits
,letters
,punctuation
, andwhitespace
.
string.
uppercase
-
A string containing all the characters that are considered uppercase letters. On most systems this is the string
'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
. The specific value is locale-dependent, and will be updated whenlocale.setlocale()
is called.
7.1.2. Custom String Formatting
New in version 2.6.
The built-in str and unicode classes provide the ability to do complex variable substitutions and value formatting via the str.format()
method described in PEP 3101 . The Formatter
class in the string
module allows you to create and customize your own string formatting behaviors using the same implementation as the built-in format()
method.
- class
string.
Formatter
-
The
Formatter
class has the following public methods:format
( format_string, *args, **kwargs )-
The primary API method. It takes a format string and an arbitrary set of positional and keyword arguments. It is just a wrapper that calls
vformat()
.
vformat
( format_string, args, kwargs )-
This function does the actual work of formatting. It is exposed as a separate function for cases where you want to pass in a predefined dictionary of arguments, rather than unpacking and repacking the dictionary as individual arguments using the
*args
and**kwargs
syntax.vformat()
does the work of breaking up the format string into character data and replacement fields. It calls the various methods described below.
In addition, the
Formatter
defines a number of methods that are intended to be replaced by subclasses:parse
( format_string )-
Loop over the format_string and return an iterable of tuples (literal_text, field_name, format_spec, conversion). This is used by
vformat()
to break the string into either literal text, or replacement fields.The values in the tuple conceptually represent a span of literal text followed by a single replacement field. If there is no literal text (which can happen if two replacement fields occur consecutively), then literal_text will be a zero-length string. If there is no replacement field, then the values of field_name, format_spec and conversion will be
None
.
get_field
( field_name, args, kwargs )-
Given field_name as returned by
parse()
(see above), convert it to an object to be formatted. Returns a tuple (obj, used_key). The default version takes strings of the form defined in PEP 3101 , such as “0[name]” or “label.title”. args and kwargs are as passed in tovformat()
. The return value used_key has the same meaning as the key parameter toget_value()
.
get_value
( key, args, kwargs )-
Retrieve a given field value. The key argument will be either an integer or a string. If it is an integer, it represents the index of the positional argument in args; if it is a string, then it represents a named argument in kwargs.
The args parameter is set to the list of positional arguments to
vformat()
, and the kwargs parameter is set to the dictionary of keyword arguments.For compound field names, these functions are only called for the first component of the field name; Subsequent components are handled through normal attribute and indexing operations.
So for example, the field expression ‘0.name’ would cause
get_value()
to be called with a key argument of 0. Thename
attribute will be looked up afterget_value()
returns by calling the built-ingetattr()
function.If the index or keyword refers to an item that does not exist, then an
IndexError
orKeyError
should be raised.
check_unused_args
( used_args, args, kwargs )-
Implement checking for unused arguments if desired. The arguments to this function is the set of all argument keys that were actually referred to in the format string (integers for positional arguments, and strings for named arguments), and a reference to the args and kwargs that was passed to vformat. The set of unused args can be calculated from these parameters.
check_unused_args()
is assumed to raise an exception if the check fails.
format_field
( value, format_spec )-
format_field()
simply calls the globalformat()
built-in. The method is provided so that subclasses can override it.
convert_field
( value, conversion )-
Converts the value (returned by
get_field()
) given a conversion type (as in the tuple returned by theparse()
method). The default version understands ‘s’ (str), ‘r’ (repr) and ‘a’ (ascii) conversion types.
7.1.3. Format String Syntax
The str.format()
method and the Formatter
class share the same syntax for format strings (although in the case of Formatter
, subclasses can define their own format string syntax).
Format strings contain “replacement fields” surrounded by curly braces {}
. Anything that is not contained in braces is considered literal text, which is copied unchanged to the output. If you need to include a brace character in the literal text, it can be escaped by doubling: {{
and }}
.
The grammar for a replacement field is as follows:
replacement_field ::= "{" [field_name
] ["!"conversion
] [":"format_spec
] "}" field_name ::= arg_name ("."attribute_name
| "["element_index
"]")* arg_name ::= [identifier
|integer
] attribute_name ::=identifier
element_index ::=integer
|index_string
index_string ::= <any source character except "]"> + conversion ::= "r" | "s" format_spec ::= <described in the next section>
In less formal terms, the replacement field can start with a field_name that specifies the object whose value is to be formatted and inserted into the output instead of the replacement field. The field_name is optionally followed by a conversion field, which is preceded by an exclamation point '!'
, and a format_spec, which is preceded by a colon ':'
. These specify a non-default format for the replacement value.
See also the Format Specification Mini-Language section.
The field_name itself begins with an arg_name that is either a number or a keyword. If it’s a number, it refers to a positional argument, and if it’s a keyword, it refers to a named keyword argument. If the numerical arg_names in a format string are 0, 1, 2, … in sequence, they can all be omitted (not just some) and the numbers 0, 1, 2, … will be automatically inserted in that order. Because arg_name is not quote-delimited, it is not possible to specify arbitrary dictionary keys (e.g., the strings '10'
or ':-]'
) within a format string. The arg_name can be followed by any number of index or attribute expressions. An expression of the form '.name'
selects the named attribute using getattr()
, while an expression of the form '[index]'
does an index lookup using __getitem__()
.
Changed in version 2.7: The positional argument specifiers can be omitted for str.format()
and unicode.format()
, so '{} {}'
is equivalent to '{0} {1}'
, u'{} {}'
is equivalent to u'{0} {1}'
.
Some simple format string examples:
"First, thou shalt count to {0}" # References first positional argument
"Bring me a {}" # Implicitly references the first positional argument
"From {} to {}" # Same as "From {0} to {1}"
"My quest is {name}" # References keyword argument 'name'
"Weight in tons {0.weight}" # 'weight' attribute of first positional arg
"Units destroyed: {players[0]}" # First element of keyword argument 'players'.
The conversion field causes a type coercion before formatting. Normally, the job of formatting a value is done by the __format__()
method of the value itself. However, in some cases it is desirable to force a type to be formatted as a string, overriding its own definition of formatting. By converting the value to a string before calling __format__()
, the normal formatting logic is bypassed.
Two conversion flags are currently supported: '!s'
which calls str()
on the value, and '!r'
which calls repr()
.
Some examples:
"Harold's a clever {0!s}" # Calls str() on the argument first
"Bring out the holy {name!r}" # Calls repr() on the argument first
The format_spec field contains a specification of how the value should be presented, including such details as field width, alignment, padding, decimal precision and so on. Each value type can define its own “formatting mini-language” or interpretation of the format_spec.
Most built-in types support a common formatting mini-language, which is described in the next section.
A format_spec field can also include nested replacement fields within it. These nested replacement fields may contain a field name, conversion flag and format specification, but deeper nesting is not allowed. The replacement fields within the format_spec are substituted before the format_spec string is interpreted. This allows the formatting of a value to be dynamically specified.
See the Format examples section for some examples.
7.1.3.1. Format Specification Mini-Language
“Format specifications” are used within replacement fields contained within a format string to define how individual values are presented (see Format String Syntax). They can also be passed directly to the built-in format()
function. Each formattable type may define how the format specification is to be interpreted.
Most built-in types implement the following options for format specifications, although some of the formatting options are only supported by the numeric types.
A general convention is that an empty format string (""
) produces the same result as if you had called str()
on the value. A non-empty format string typically modifies the result.
The general form of a standard format specifier is:
format_spec ::= [[fill
]align
][sign
][#][0][width
][,][.precision
][type
] fill ::= <any character> align ::= "<" | ">" | "=" | "^" sign ::= "+" | "-" | " " width ::=integer
precision ::=integer
type ::= "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"
If a valid align value is specified, it can be preceded by a fill character that can be any character and defaults to a space if omitted. It is not possible to use a literal curly brace (“{
” or “}
”) as the fill character when using the str.format()
method. However, it is possible to insert a curly brace with a nested replacement field. This limitation doesn’t affect the format()
function.
The meaning of the various alignment options is as follows:
Option
Meaning
'<'
Forces the field to be left-aligned within the available space (this is the default for most objects).
'>'
Forces the field to be right-aligned within the available space (this is the default for numbers).
'='
Forces the padding to be placed after the sign (if any) but before the digits. This is used for printing fields in the form ‘+000000120’. This alignment option is only valid for numeric types. It becomes the default when ‘0’ immediately precedes the field width.
'^'
Forces the field to be centered within the available space.
Note that unless a minimum field width is defined, the field width will always be the same size as the data to fill it, so that the alignment option has no meaning in this case.
The sign option is only valid for number types, and can be one of the following:
Option
Meaning
'+'
indicates that a sign should be used for both positive as well as negative numbers.
'-'
indicates that a sign should be used only for negative numbers (this is the default behavior).
space
indicates that a leading space should be used on positive numbers, and a minus sign on negative numbers.
The '#'
option is only valid for integers, and only for binary, octal, or hexadecimal output. If present, it specifies that the output will be prefixed by '0b'
, '0o'
, or '0x'
, respectively.
The ','
option signals the use of a comma for a thousands separator. For a locale aware separator, use the 'n'
integer presentation type instead.
Changed in version 2.7: Added the ','
option (see also PEP 378 ).
width is a decimal integer defining the minimum field width. If not specified, then the field width will be determined by the content.
When no explicit alignment is given, preceding the width field by a zero ('0'
) character enables sign-aware zero-padding for numeric types. This is equivalent to a fill character of '0'
with an alignment type of '='
.
The precision is a decimal number indicating how many digits should be displayed after the decimal point for a floating point value formatted with 'f'
and 'F'
, or before and after the decimal point for a floating point value formatted with 'g'
or 'G'
. For non-number types the field indicates the maximum field size - in other words, how many characters will be used from the field content. The precision is not allowed for integer values.
Finally, the type determines how the data should be presented.
The available string presentation types are:
Type
Meaning
's'
String format. This is the default type for strings and may be omitted.
None
The same as
's'
.
The available integer presentation types are:
Type
Meaning
'b'
Binary format. Outputs the number in base 2.
'c'
Character. Converts the integer to the corresponding unicode character before printing.
'd'
Decimal Integer. Outputs the number in base 10.
'o'
Octal format. Outputs the number in base 8.
'x'
Hex format. Outputs the number in base 16, using lower- case letters for the digits above 9.
'X'
Hex format. Outputs the number in base 16, using upper- case letters for the digits above 9.
'n'
Number. This is the same as
'd'
, except that it uses the current locale setting to insert the appropriate number separator characters.None
The same as
'd'
.
In addition to the above presentation types, integers can be formatted with the floating point presentation types listed below (except 'n'
and None
). When doing so, float()
is used to convert the integer to a floating point number before formatting.
The available presentation types for floating point and decimal values are:
Type
Meaning
'e'
Exponent notation. Prints the number in scientific notation using the letter ‘e’ to indicate the exponent. The default precision is
6
.
'E'
Exponent notation. Same as
'e'
except it uses an upper case ‘E’ as the separator character.
'f'
Fixed-point notation. Displays the number as a fixed-point number. The default precision is
6
.
'F'
Fixed point notation. Same as
'f'
.
'g'
General format. For a given precision
p >= 1
, this rounds the number top
significant digits and then formats the result in either fixed-point format or in scientific notation, depending on its magnitude.The precise rules are as follows: suppose that the result formatted with presentation type
'e'
and precisionp-1
would have exponentexp
. Then if-4 <= exp < p
, the number is formatted with presentation type'f'
and precisionp-1-exp
. Otherwise, the number is formatted with presentation type'e'
and precisionp-1
. In both cases insignificant trailing zeros are removed from the significand, and the decimal point is also removed if there are no remaining digits following it.Positive and negative infinity, positive and negative zero, and nans, are formatted as
inf
,-inf
,0
,-0
andnan
respectively, regardless of the precision.A precision of
0
is treated as equivalent to a precision of1
. The default precision is6
.
'G'
General format. Same as
'g'
except switches to'E'
if the number gets too large. The representations of infinity and NaN are uppercased, too.
'n'
Number. This is the same as
'g'
, except that it uses the current locale setting to insert the appropriate number separator characters.
'%'
Percentage. Multiplies the number by 100 and displays in fixed (
'f'
) format, followed by a percent sign.None
The same as
'g'
.
7.1.3.2. Format examples
This section contains examples of the str.format()
syntax and comparison with the old %
-formatting.
In most of the cases the syntax is similar to the old %
-formatting, with the addition of the {}
and with :
used instead of %
. For example, '%03.2f'
can be translated to '{:03.2f}'
.
The new format syntax also supports new and different options, shown in the following examples.
Accessing arguments by position:
>>> '{0}, {1}, {2}'.format('a', 'b', 'c')
'a, b, c'
>>> '{}, {}, {}'.format('a', 'b', 'c') # 2.7+ only
'a, b, c'
>>> '{2}, {1}, {0}'.format('a', 'b', 'c')
'c, b, a'
>>> '{2}, {1}, {0}'.format(*'abc') # unpacking argument sequence
'c, b, a'
>>> '{0}{1}{0}'.format('abra', 'cad') # arguments' indices can be repeated
'abracadabra'
Accessing arguments by name:
>>> 'Coordinates: {latitude}, {longitude}'.format(latitude='37.24N', longitude='-115.81W')
'Coordinates: 37.24N, -115.81W'
>>> coord = {'latitude': '37.24N', 'longitude': '-115.81W'}
>>> 'Coordinates: {latitude}, {longitude}'.format(**coord)
'Coordinates: 37.24N, -115.81W'
Accessing arguments’ attributes:
>>> c = 3-5j
>>> ('The complex number {0} is formed from the real part {0.real} '
... 'and the imaginary part {0.imag}.').format(c)
'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.'
>>> class Point(object):
... def __init__(self, x, y):
... self.x, self.y = x, y
... def __str__(self):
... return 'Point({self.x}, {self.y})'.format(self=self)
...
>>> str(Point(4, 2))
'Point(4, 2)'
Accessing arguments’ items:
>>> coord = (3, 5)
>>> 'X: {0[0]}; Y: {0[1]}'.format(coord)
'X: 3; Y: 5'
Replacing %s
and %r
:
>>> "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2')
"repr() shows quotes: 'test1'; str() doesn't: test2"
Aligning the text and specifying a width:
>>> '{:<30}'.format('left aligned')
'left aligned '
>>> '{:>30}'.format('right aligned')
' right aligned'
>>> '{:^30}'.format('centered')
' centered '
>>> '{:*^30}'.format('centered') # use '*' as a fill char
'***********centered***********'
Replacing %+f
, %-f
, and % f
and specifying a sign:
>>> '{:+f}; {:+f}'.format(3.14, -3.14) # show it always
'+3.140000; -3.140000'
>>> '{: f}; {: f}'.format(3.14, -3.14) # show a space for positive numbers
' 3.140000; -3.140000'
>>> '{:-f}; {:-f}'.format(3.14, -3.14) # show only the minus -- same as '{:f}; {:f}'
'3.140000; -3.140000'
Replacing %x
and %o
and converting the value to different bases:
>>> # format also supports binary numbers
>>> "int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}".format(42)
'int: 42; hex: 2a; oct: 52; bin: 101010'
>>> # with 0x, 0o, or 0b as prefix:
>>> "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}".format(42)
'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'
Using the comma as a thousands separator:
>>> '{:,}'.format(1234567890)
'1,234,567,890'
Expressing a percentage:
>>> points = 19.5
>>> total = 22
>>> 'Correct answers: {:.2%}'.format(points/total)
'Correct answers: 88.64%'
Using type-specific formatting:
>>> import datetime
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
>>> '{:%Y-%m-%d %H:%M:%S}'.format(d)
'2010-07-04 12:15:58'
Nesting arguments and more complex examples:
>>> for align, text in zip('<^>', ['left', 'center', 'right']):
... '{0:{fill}{align}16}'.format(text, fill=align, align=align)
...
'left<<<<<<<<<<<<'
'^^^^^center^^^^^'
'>>>>>>>>>>>right'
>>>
>>> octets = [192, 168, 0, 1]
>>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)
'C0A80001'
>>> int(_, 16)
3232235521
>>>
>>> width = 5
>>> for num in range(5,12):
... for base in 'dXob':
... print '{0:{width}{base}}'.format(num, base=base, width=width),
... print
...
5 5 5 101
6 6 6 110
7 7 7 111
8 8 10 1000
9 9 11 1001
10 A 12 1010
11 B 13 1011
7.1.4. Template strings
New in version 2.4.
Templates provide simpler string substitutions as described in PEP 292 . Instead of the normal %
-based substitutions, Templates support $
-based substitutions, using the following rules:
$$
is an escape; it is replaced with a single$
.$identifier
names a substitution placeholder matching a mapping key of"identifier"
. By default,"identifier"
must spell a Python identifier. The first non-identifier character after the$
character terminates this placeholder specification.${identifier}
is equivalent to$identifier
. It is required when valid identifier characters follow the placeholder but are not part of the placeholder, such as"${noun}ification"
.
Any other appearance of $
in the string will result in a ValueError
being raised.
The string
module provides a Template
class that implements these rules. The methods of Template
are:
- class
string.
Template
( template ) -
The constructor takes a single argument which is the template string.
substitute
( mapping [, **kws ] )-
Performs the template substitution, returning a new string. mapping is any dictionary-like object with keys that match the placeholders in the template. Alternatively, you can provide keyword arguments, where the keywords are the placeholders. When both mapping and kws are given and there are duplicates, the placeholders from kws take precedence.
safe_substitute
( mapping [, **kws ] )-
Like
substitute()
, except that if placeholders are missing from mapping and kws, instead of raising aKeyError
exception, the original placeholder will appear in the resulting string intact. Also, unlike withsubstitute()
, any other appearances of the$
will simply return$
instead of raisingValueError
.While other exceptions may still occur, this method is called “safe” because it always tries to return a usable string instead of raising an exception. In another sense,
safe_substitute()
may be anything other than safe, since it will silently ignore malformed templates containing dangling delimiters, unmatched braces, or placeholders that are not valid Python identifiers.
Template
instances also provide one public data attribute:
Here is an example of how to use a Template:
>>> from string import Template
>>> s = Template('$who likes $what')
>>> s.substitute(who='tim', what='kung pao')
'tim likes kung pao'
>>> d = dict(who='tim')
>>> Template('Give $who $100').substitute(d)
Traceback (most recent call last):
...
ValueError: Invalid placeholder in string: line 1, col 11
>>> Template('$who likes $what').substitute(d)
Traceback (most recent call last):
...
KeyError: 'what'
>>> Template('$who likes $what').safe_substitute(d)
'tim likes $what'
Advanced usage: you can derive subclasses of Template
to customize the placeholder syntax, delimiter character, or the entire regular expression used to parse template strings. To do this, you can override these class attributes:
delimiter – This is the literal string describing a placeholder introducing delimiter. The default value is
$
. Note that this should not be a regular expression, as the implementation will callre.escape()
on this string as needed.idpattern – This is the regular expression describing the pattern for non-braced placeholders (the braces will be added automatically as appropriate). The default value is the regular expression
[_a-z][_a-z0-9]*
.
Alternatively, you can provide the entire regular expression pattern by overriding the class attribute pattern. If you do this, the value must be a regular expression object with four named capturing groups. The capturing groups correspond to the rules given above, along with the invalid placeholder rule:
escaped – This group matches the escape sequence, e.g.
$$
, in the default pattern.named – This group matches the unbraced placeholder name; it should not include the delimiter in capturing group.
braced – This group matches the brace enclosed placeholder name; it should not include either the delimiter or braces in the capturing group.
invalid – This group matches any other delimiter pattern (usually a single delimiter), and it should appear last in the regular expression.
7.1.5. String functions
The following functions are available to operate on string and Unicode objects. They are not available as string methods.
string.
capwords
( s [, sep ] )-
Split the argument into words using
str.split()
, capitalize each word usingstr.capitalize()
, and join the capitalized words usingstr.join()
. If the optional second argument sep is absent orNone
, runs of whitespace characters are replaced by a single space and leading and trailing whitespace are removed, otherwise sep is used to split and join the words.
string.
maketrans
( from, to )-
Return a translation table suitable for passing to
translate()
, that will map each character in from into the character at the same position in to; from and to must have the same length.Note
Don’t use strings derived from
lowercase
anduppercase
as arguments; in some locales, these don’t have the same length. For case conversions, always usestr.lower()
andstr.upper()
.
7.1.6. Deprecated string functions
The following list of functions are also defined as methods of string and Unicode objects; see section String Methods for more information on those. You should consider these functions as deprecated, although they will not be removed until Python 3. The functions defined in this module are:
string.
atof
( s )-
Deprecated since version 2.0: Use the
float()
built-in function.Convert a string to a floating point number. The string must have the standard syntax for a floating point literal in Python, optionally preceded by a sign (
+
or-
). Note that this behaves identical to the built-in functionfloat()
when passed a string.Note
When passing in a string, values for NaN and Infinity may be returned, depending on the underlying C library. The specific set of strings accepted which cause these values to be returned depends entirely on the C library and is known to vary.
string.
atoi
( s [, base ] )-
Deprecated since version 2.0: Use the
int()
built-in function.Convert string s to an integer in the given base. The string must consist of one or more digits, optionally preceded by a sign (
+
or-
). The base defaults to 10. If it is 0, a default base is chosen depending on the leading characters of the string (after stripping the sign):0x
or0X
means 16,0
means 8, anything else means 10. If base is 16, a leading0x
or0X
is always accepted, though not required. This behaves identically to the built-in functionint()
when passed a string. (Also note: for a more flexible interpretation of numeric literals, use the built-in functioneval()
.)
string.
atol
( s [, base ] )-
Deprecated since version 2.0: Use the
long()
built-in function.Convert string s to a long integer in the given base. The string must consist of one or more digits, optionally preceded by a sign (
+
or-
). The base argument has the same meaning as foratoi()
. A trailingl
orL
is not allowed, except if the base is 0. Note that when invoked without base or with base set to 10, this behaves identical to the built-in functionlong()
when passed a string.
string.
expandtabs
( s [, tabsize ] )-
Expand tabs in a string replacing them by one or more spaces, depending on the current column and the given tab size. The column number is reset to zero after each newline occurring in the string. This doesn’t understand other non-printing characters or escape sequences. The tab size defaults to 8.
string.
find
( s, sub [, start [, end ] ] )-
Return the lowest index in s where the substring sub is found such that sub is wholly contained in
s[start:end]
. Return-1
on failure. Defaults for start and end and interpretation of negative values is the same as for slices.
string.
rfind
( s, sub [, start [, end ] ] )-
Like
find()
but find the highest index.
string.
index
( s, sub [, start [, end ] ] )-
Like
find()
but raiseValueError
when the substring is not found.
string.
rindex
( s, sub [, start [, end ] ] )-
Like
rfind()
but raiseValueError
when the substring is not found.
string.
count
( s, sub [, start [, end ] ] )-
Return the number of (non-overlapping) occurrences of substring sub in string
s[start:end]
. Defaults for start and end and interpretation of negative values are the same as for slices.
string.
split
( s [, sep [, maxsplit ] ] )-
Return a list of the words of the string s. If the optional second argument sep is absent or
None
, the words are separated by arbitrary strings of whitespace characters (space, tab, newline, return, formfeed). If the second argument sep is present and notNone
, it specifies a string to be used as the word separator. The returned list will then have one more item than the number of non-overlapping occurrences of the separator in the string. If maxsplit is given, at most maxsplit number of splits occur, and the remainder of the string is returned as the final element of the list (thus, the list will have at mostmaxsplit+1
elements). If maxsplit is not specified or-1
, then there is no limit on the number of splits (all possible splits are made).The behavior of split on an empty string depends on the value of sep. If sep is not specified, or specified as
None
, the result will be an empty list. If sep is specified as any string, the result will be a list containing one element which is an empty string.
string.
rsplit
( s [, sep [, maxsplit ] ] )-
Return a list of the words of the string s, scanning s from the end. To all intents and purposes, the resulting list of words is the same as returned by
split()
, except when the optional third argument maxsplit is explicitly specified and nonzero. If maxsplit is given, at most maxsplit number of splits – the rightmost ones – occur, and the remainder of the string is returned as the first element of the list (thus, the list will have at mostmaxsplit+1
elements).New in version 2.4.
string.
splitfields
( s [, sep [, maxsplit ] ] )-
This function behaves identically to
split()
. (In the past,split()
was only used with one argument, whilesplitfields()
was only used with two arguments.)
string.
join
( words [, sep ] )-
Concatenate a list or tuple of words with intervening occurrences of sep. The default value for sep is a single space character. It is always true that
string.join(string.split(s, sep), sep)
equals s.
string.
joinfields
( words [, sep ] )-
This function behaves identically to
join()
. (In the past,join()
was only used with one argument, whilejoinfields()
was only used with two arguments.) Note that there is nojoinfields()
method on string objects; use thejoin()
method instead.
string.
lstrip
( s [, chars ] )-
Return a copy of the string with leading characters removed. If chars is omitted or
None
, whitespace characters are removed. If given and notNone
, chars must be a string; the characters in the string will be stripped from the beginning of the string this method is called on.Changed in version 2.2.3: The chars parameter was added. The chars parameter cannot be passed in earlier 2.2 versions.
string.
rstrip
( s [, chars ] )-
Return a copy of the string with trailing characters removed. If chars is omitted or
None
, whitespace characters are removed. If given and notNone
, chars must be a string; the characters in the string will be stripped from the end of the string this method is called on.Changed in version 2.2.3: The chars parameter was added. The chars parameter cannot be passed in earlier 2.2 versions.
string.
strip
( s [, chars ] )-
Return a copy of the string with leading and trailing characters removed. If chars is omitted or
None
, whitespace characters are removed. If given and notNone
, chars must be a string; the characters in the string will be stripped from the both ends of the string this method is called on.Changed in version 2.2.3: The chars parameter was added. The chars parameter cannot be passed in earlier 2.2 versions.
string.
swapcase
( s )-
Return a copy of s, but with lower case letters converted to upper case and vice versa.
string.
translate
( s, table [, deletechars ] )-
Delete all characters from s that are in deletechars (if present), and then translate the characters using table, which must be a 256-character string giving the translation for each character value, indexed by its ordinal. If table is
None
, then only the character deletion step is performed.
string.
ljust
( s, width [, fillchar ] )string.
rjust
( s, width [, fillchar ] )string.
center
( s, width [, fillchar ] )-
These functions respectively left-justify, right-justify and center a string in a field of given width. They return a string that is at least width characters wide, created by padding the string s with the character fillchar (default is a space) until the given width on the right, left or both sides. The string is never truncated.