pipes — Interface to shell pipelines

Source code: Lib/pipes.py

The pipes module defines a class to abstract the concept of a pipeline — a sequence of converters from one file to another.

Because the module uses /bin/sh command lines, a POSIX or compatible shell for os.system() and os.popen() is required.

The pipes module defines the following class:

class pipes. Template

An abstraction of a pipeline.


>>> import pipes
>>> t = pipes.Template()
>>> t.append('tr a-z A-Z', '--')
>>> f = t.open('pipefile', 'w')
>>> f.write('hello world')
>>> f.close()
>>> open('pipefile').read()

Template Objects

Template objects following methods:

Template. reset ( )

Restore a pipeline template to its initial state.

Template. clone ( )

Return a new, equivalent, pipeline template.

Template. debug ( flag )

If flag is true, turn debugging on. Otherwise, turn debugging off. When debugging is on, commands to be executed are printed, and the shell is given set -x command to be more verbose.

Template. append ( cmd, kind )

Append a new action at the end. The cmd variable must be a valid bourne shell command. The kind variable consists of two letters.

The first letter can be either of '-' (which means the command reads its standard input), 'f' (which means the commands reads a given file on the command line) or '.' (which means the commands reads no input, and hence must be first.)

Similarly, the second letter can be either of '-' (which means the command writes to standard output), 'f' (which means the command writes a file on the command line) or '.' (which means the command does not write anything, and hence must be last.)

Template. prepend ( cmd, kind )

Add a new action at the beginning. See append() for explanations of the arguments.

Template. open ( file, mode )

Return a file-like object, open to file, but read from or written to by the pipeline. Note that only one of 'r', 'w' may be given.

Template. copy ( infile, outfile )

Copy infile to outfile through the pipe.