all Python 3Files & I/Ofunction

io.IOBase.writelines()

writing

Write every string from an iterable in sequence; it adds no separators, so '\n' must already be in the strings or everything runs together.

Syntax

f.writelines(lines)

The name misleads: the method knows nothing about "lines", it just calls write() on each item in turn. It pairs with readlines(), which keeps the '\n' inside each item, so f_out.writelines(f_in.readlines()) keeps the line structure (byte for byte only in binary mode: text mode turns '\r\n' into '\n' on reading) — but after splitlines() or strip() you have to put the newlines back yourself. Any iterable works as input, including a generator or another file object; in binary mode the items must be bytes or you get a TypeError.

Examples

lines = ['line1\n', 'line2\n', 'line3\n']
with open('out2.txt', 'w') as f:
    f.writelines(lines)
with open('out3.txt', 'w') as f:
    f.writelines(f'{i}\n' for i in range(5))

See also

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