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Python standard library: io

The io module provides interfaces to stream handling.

Among others, this module defines the built-in function open.

dir(io)

import io
for e in sorted(dir(io), key=lambda s: s.lower()): print(e)

`__all__`
`__author__`
`__builtins__`
`__cached__`
`__doc__`
`__file__`
`__getattr__`
`__loader__`
`__name__`
`__package__`
`__spec__`
`_io`
`_WindowsConsoleIO`
`abc`
`BlockingIOError`
`BufferedIOBase`
`BufferedRandom`
`BufferedReader`
`BufferedRWPair`
`BufferedWriter`
`BytesIO`
`DEFAULT_BUFFER_SIZE`
`FileIO`
`IncrementalNewlineDecoder`
`IOBase`
`open`
`open_code`
`RawIOBase`
`SEEK_CUR`
`SEEK_END`
`SEEK_SET`
`StringIO`	The `StringIO` class creates a «file-like» object from a string, which allows to read from it as if it were a file. Compare with `csv.StringIO`.
`text_encoding`
`TextIOBase`
`TextIOWrapper`
`UnsupportedOperation`

File objects

Python deals with three kinds of file objects.

binary files
buffered binary files
text files

These interfaces are defined in the io module.

StringIO

In Python, strings are immutable. So they cannot be modified in-place.

However, with the io module, such an in-place modification can be simulated with StringIO():

import io

txt = 'Hello world!'

txt_io = io.StringIO(txt)

print(txt_io.getvalue())

txt_io.seek(6)
txt_io.write('there')

print(txt_io.getvalue())

Github repository about-Python, path: /standard-library/io/StringIO.py

This example is from the Python FAQ.

open

io.open() is the same function as the built-in function open().

open binary vs open text

with open(__file__, 'r')  as f:
     print_type(f)

with open(__file__, 'rb') as f:
     print_type(f)

with open('/tmp/a', 'w' ) as f:
     print_type(f)

with open('/tmp/a', 'wb') as f:
     print_type(f)

This script prints:

_io.TextIOWrapper
  _io.TextIOWrapper <- _io._TextIOBase <- _io._IOBase <- builtins.object
_io.BufferedReader
  _io.BufferedReader <- _io._BufferedIOBase <- _io._IOBase <- builtins.object
_io.TextIOWrapper
  _io.TextIOWrapper <- _io._TextIOBase <- _io._IOBase <- builtins.object
_io.BufferedWriter
  _io.BufferedWriter <- _io._BufferedIOBase <- _io._IOBase <- builtins.object

Slurp content of file into a variable

The content of an entire file can easily be read into a variable with the following construct. __file__ needs to be replaced with the filename to be read:

with open (__file__, 'r') as f:
     text = f.read()

print(text)