replace-stdout-stderr (UP022)

Derived from the pyupgrade linter.

Fix is sometimes available.

What it does

Checks for uses of subprocess.run that send stdout and stderr to a pipe.

Why is this bad?

As of Python 3.7, subprocess.run has a capture_output keyword argument that can be set to True to capture stdout and stderr outputs. This is equivalent to setting stdout and stderr to subprocess.PIPE, but is more explicit and readable.

Example

import subprocess

subprocess.run(["foo"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)

Use instead:

import subprocess

subprocess.run(["foo"], capture_output=True)

References

• Python 3.7 release notes
• Python documentation: subprocess.run