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io.BufferedWriter

binary streams

A buffered binary write stream wrapping a raw stream; flushes in batches.

Syntax

io.BufferedWriter(raw)

Until the buffer fills up, whatever you wrote lives in process memory: if the program crashes or the stream is never closed, the file ends up empty or truncated, which is why you open it with a with-block. flush() hands the bytes to the operating system but does not guarantee they reached the physical disk — that takes os.fsync() on the descriptor. The wrapped raw stream must be writable; use BufferedReader for reading and BufferedRandom when you need both.

Examples

import io
raw = io.BytesIO()
w = io.BufferedWriter(raw)
w.write(b'hi')
w.flush()
print(raw.getvalue())   # → b'hi'

See also

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