Python 3.13+Windowsosfunction

os.path.isreserved()

os.path — existence and type checks

Checks whether a pathname is reserved on the current system: on Windows these are NUL, CON, COM1, names with colons, wildcards, or a trailing dot/space. Windows only, Python 3.13+.

Syntax

os.path.isreserved(path)

It matters when creating files from user-supplied names on Windows: a file named CON or NUL cannot be created, and writing to such a path goes to a device. Every component of the path is checked. Such a name can be saved with a prefix or an alteration — check before creating the file, not after an error.

Examples

import os, ntpath
print(not hasattr(os.path, 'isreserved') or callable(os.path.isreserved))   # → True
print(ntpath.isreserved('NUL'))   # → True
print(ntpath.isreserved('COM1'))   # → True
print(ntpath.isreserved('report.'))   # → True
print(ntpath.isreserved('report.txt'))   # → False

See also

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