Skip to content

bad-open-mode (PLW1501)

Added in 0.5.0 · Related issues · View source

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:
    content = f.read()

Use instead:

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

References