MutaPath.in_place(mode='r', buffering=-1, encoding=None, errors=None, newline=None, backup_extension=None)[source]

A context in which a file may be re-written in-place with new content.

Yields a tuple of (readable, writable) file objects, where writable replaces readable.

If an exception occurs, the old file is restored, removing the written data.

Mode must not use 'w', 'a', or '+'; only read-only-modes are allowed. A ValueError is raised on invalid modes.

For example, to add line numbers to a file:

p = Path(filename)
assert p.isfile()
with p.in_place() as (reader, writer):
    for number, line in enumerate(reader, 1):
        writer.write('{0:3}: '.format(number)))

Thereafter, the file at filename will have line numbers in it.