shallow-copy-environ (PLW1507)

Added in 0.10.0 · Related issues · View source

Derived from the Pylint linter.

Fix is always available.

What it does

Check for shallow os.environ copies.

Why is this bad?

os.environ is not a dict object, but rather, a proxy object. As such, mutating a shallow copy of os.environ will also mutate the original object.

See BPO 15373 for more information.

Example

import copy
import os

env = copy.copy(os.environ)

Use instead:

import os

env = os.environ.copy()

Fix safety

This rule's fix is marked as unsafe because replacing a shallow copy with a deep copy can lead to unintended side effects. If the program modifies the shallow copy at some point, changing it to a deep copy may prevent those modifications from affecting the original data, potentially altering the program's behavior.

References

• Python documentation: copy — Shallow and deep copy operations
• Python documentation: os.environ