python-gotchas
Installation
SKILL.md
Quick Reference
| Gotcha | Problem | Fix |
|---|---|---|
| Mutable default | def f(x=[]) |
Use None, create in function |
| Iterate + mutate | Skips items | Iterate over copy items[:] |
is vs == |
Identity vs value | Use is only for None |
| Late binding | lambda: i captures var |
lambda i=i: i |
| Float precision | 0.1 + 0.2 != 0.3 |
math.isclose() |
| Dict mutation | RuntimeError | list(d.keys()) |
| Class attribute | Shared mutable | Init in __init__ |
| Falsy Values | Examples |
|---|---|
| Boolean | False |
| None | None |
| Numbers | 0, 0.0, 0j |
| Empty collections | "", [], {}, set() |