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The default argument is mutable

Reports a problem when a mutable value as a list or dictionary is detected in a default value for an argument.

Default argument values are evaluated only once at function definition time, which means that modifying the default value of the argument will affect all subsequent calls of that function.


def func(s, cache={}): cache[s] = None

When the quick-fix is applied, the code changes to:

def func(s, cache=None): if cache is None: cache = {} cache[s] = None

Inspection Details

By default bundled with:

DataSpell 2024.1, IntelliJ IDEA 2024.1, PyCharm 2024.1, Qodana for JVM 2024.1,

Can be installed with plugin:

Python Community Edition, 241.SNAPSHOT

Last modified: 29 April 2024