pytb.io module

Redirecting output streams

The io Module offers function to temporarly redirect or mirror stdout and stderr streams to a file

Stream redirection:

>>> from pytb.io import redirected_stdout
>>> with redirected_stdout('stdout.txt'):
...     print('this will be written to stdout.txt and not to the console')

Stream mirroring

>>> from pytb.io import mirrored_stdstreams
>>> with mirrored_stdstreams('alloutput.txt'):
...     print('this will be written to alloutput.txt AND to the console')

API Documentation

This module contains a set of helpers for common Input/Output related tasks

class pytb.io.Tee(*args)

Bases: object

A N-ended T-piece (manifold) for File objects that supports writing. This is useful if you want to write to multiple files or file-like objects (e.g. sys.stdout, sys.stderr) simultaneously.

>>> import sys, io
>>> file_like = io.StringIO()
>>> combined = Tee(file_like, sys.stdout)
>>> _ = combined.write('This is printed into a file and on stdout\n')
This is printed into a file and on stdout
>>> assert file_like.getvalue() == 'This is printed into a file and on stdout\n'

close() → None

Close all connected files

This does avoid closing sys.__stdout__ and sys.__stderr__

>>> import sys, io
>>> file_like = io.StringIO()
>>> combined = Tee(file_like, sys.__stdout__)
>>> file_like.closed
False
>>> combined.close()
>>> file_like.closed
True
>>> sys.stdout.closed
False

flush() → None

Flush any buffers of all connected file output-streams

write(text: str) → int

Write to the manifold which, in turn, writes to all connected output streams

Parameters:text – text to write to the manifold Returns:the number of bytes written to the last stream in the Manifold

pytb.io.mirrored_stdout(file: Union[str, TextIO, pytb.io.Tee]) → Generator[TextIO, None, None]

ContextManager that mirrors stdout to a given file-like object and restores the original state when leaving the context

This is essentially using a Tee piece manifold to file and sys.stdout as a parameter to redirected_stdout

Parameters:file – string or file-like object to mirror stdout to. If passed a string, the file is opened for writing and closed after the contextmanager exits

>>> import io
>>> outfile = io.StringIO()
>>> with mirrored_stdout(outfile):
...     print('this is written to outfile and stdout')
this is written to outfile and stdout
>>> assert outfile.getvalue() == 'this is written to outfile and stdout\n'

pytb.io.mirrored_stdstreams(file: Union[str, TextIO, pytb.io.Tee]) → Generator[TextIO, None, None]

Version of mirrored_stdout() but mirrors stderr and stdout to file

see mirrored_stdout()

pytb.io.redirected_stderr(file: Union[str, TextIO, pytb.io.Tee]) → Generator[TextIO, None, None]

Same functionality as redirect_stdout but redirects the stderr stram instead

see redirected_stdout()

pytb.io.redirected_stdout(file: Union[str, TextIO, pytb.io.Tee]) → Generator[TextIO, None, None]

ContextManager that redirects stdout to a given file-like object and restores the original state when leaving the context

Parameters:file – string or file-like object to redirect stdout to. If passed a string, the file is opened for writing and closed after the contextmanager exits

>>> import io
>>> outfile = io.StringIO()
>>> with redirected_stdout(outfile):
...     print('this is written to outfile')
>>> assert outfile.getvalue() == 'this is written to outfile\n'

pytb.io.redirected_stdstreams(file: Union[str, TextIO, pytb.io.Tee]) → Generator[TextIO, None, None]

redirects both output streams (stderr and stdout) to file

see redirected_stdout()

pytb.io.render_text(text: str, maxwidth: int = -1) → str

Attempt to render a text like an (potentiall infinitely wide) terminal would.

Thus carriage-returns move the cursor to the start of the line, so subsequent characters overwrite the previous.

>>> render_text('asd\rbcd\rcde\r\nqwe\rert\n123', maxwidth=2)
'cd\ne \ner\nt \n12\n3'

Parameters:

• text – Input text to render
• maxwidth – if > 0, wrap the text to the specified maximum length using the textwrapper library