When is the use of
len(SEQ)as a condition value problematic? What major
situations is Pylint attempting to avoid with C1801?
It’s not really problematic to use len(SEQUENCE) – though it may not be as efficient (see chepner’s comment). Regardless, Pylint checks code for compliance with the PEP 8 style guide which states that
For sequences, (strings, lists, tuples), use the fact that empty sequences are false.
Yes: if not seq: if seq: No: if len(seq): if not len(seq):
As an occasional Python programmer, who flits between languages, I’d consider the len(SEQUENCE) construct to be more readable and explicit (“Explicit is better then implicit”). However, using the fact that an empty sequence evaluates to False in a Boolean context is considered more “Pythonic”.