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io.FileIO

binary streams

A raw (unbuffered) binary stream to a file by name or descriptor; the low-level base on which open() builds buffering.

Syntax

io.FileIO(name, mode='r')

You rarely construct it yourself: open(path, 'rb', buffering=0) hands you exactly a FileIO, and a normal open() stacks buffering and text decoding on top of one. The classic trap with a raw stream is that read(n) issues a single system call and may legitimately return fewer than n bytes long before EOF, so read with readall() or loop until you get an empty result.

Examples

import io
import os
print(issubclass(io.FileIO, io.RawIOBase))   # → True
f = io.FileIO(os.devnull, 'r')
print(f.mode)   # → rb
print(f.readable(), f.writable())   # → True False
print(f.read())   # → b''
f.close()
print(f.closed)   # → True
b = open(os.devnull, 'rb')
print(type(b.raw).__name__)   # → FileIO
b.close()

See also

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