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multiple-starts-ends-with (PIE810)#

Derived from the flake8-pie linter.

Fix is always available.

What it does#

Checks for startswith or endswith calls on the same value with different prefixes or suffixes.

Why is this bad?#

The startswith and endswith methods accept tuples of prefixes or suffixes respectively. Passing a tuple of prefixes or suffixes is more efficient and readable than calling the method multiple times.


msg = "Hello, world!"
if msg.startswith("Hello") or msg.startswith("Hi"):

Use instead:

msg = "Hello, world!"
if msg.startswith(("Hello", "Hi")):

Fix safety#

This rule's fix is unsafe, as in some cases, it will be unable to determine whether the argument to an existing .startswith or .endswith call is a tuple. For example, given msg.startswith(x) or msg.startswith(y), if x or y is a tuple, and the semantic model is unable to detect it as such, the rule will suggest msg.startswith((x, y)), which will error at runtime.