Anti-Patterns in Python Programming

Abstraction: Common Python beginner mistakes and idiomatic alternatives

Key points:

• Avoid range() for simple sequence iteration; use the for-in construct directly; off-by-one bugs are common with range(len(x))
• Prefer list comprehensions over loop-plus-append; can handle nesting and conditionals inline
• Use sets (not lists) for repeated membership testing: set lookup is O(1) vs O(n) for lists; build the set once outside the loop
• Loop variables leak into the enclosing scope in Python (unlike Java); initialize sentinel variables (preferably None) before loops to avoid NameError on empty sequences
• Keep outer scope (global namespace) to IN_ALL_CAPS constants; delegate everything else to functions to avoid accidental global variable capture
• Use is (not ==) when testing for None; follow PEP 8; test empty containers with plain if x: not len(x) > 0

Connections: Python · Python Best Practices · Code Quality · Software Engineering

Source: http://lignos.org/py_antipatterns/