Metadata

ID: python-best-practices/invalid-assert

Language: Python

Severity: Notice

Category: Best Practices

Description

In Python, non-empty strings and non-empty tuples are considered True in a boolean context. Therefore, assert "Something bad happened" and assert (foo, bar) will always evaluate to True, even if foo and bar are False or None. This means that these assertions will never fail and are therefore invalid.

To avoid this, make sure that the expression after the assert keyword is a boolean expression that can evaluate to either True or False. For example, instead of assert "Something bad happened", you could use assert foo is not None, "Something bad happened". This will raise an AssertionError with the message “Something bad happened” if foo is None. Similarly, instead of assert (foo, bar), you could use assert foo == bar to check if foo and bar are equal.

Non-Compliant Code Examples

assert "Something bad happened"
assert (foo, bar)

Compliant Code Examples

assert foo == bar
assert booleanValue
assert portId.isnumeric(), "portId must be numeric"

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