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bad-open-mode (PLW1501)#

Derived from the Pylint linter.

What it does#

Check for an invalid mode argument in open calls.

Why is this bad?#

The open function accepts a mode argument that specifies how the file should be opened (e.g., read-only, write-only, append-only, etc.).

Python supports a variety of open modes: r, w, a, and x, to control reading, writing, appending, and creating, respectively, along with b (binary mode), + (read and write), and U (universal newlines), the latter of which is only valid alongside r. This rule detects both invalid combinations of modes and invalid characters in the mode string itself.

Example#

with open("file", "rwx") as f:
    return f.read()

Use instead:

with open("file", "r") as f:
    return f.read()

References#