metadata:
  version: "1.0.0"
  last_updated: "2026-02-01"
  source_urls: []

category: language-specific
subcategory: python
tier: T2

bugs_caught:
  - "Python-specific gotchas"
  - "Mutable default arguments"
  - "None vs False confusion"

values:
  # None vs False
  none_vs_false:
    comparisons:
      - expr: "None == False"
        result: "False"
      - expr: "not None"
        result: "True"
      - expr: "bool(None)"
        result: "False"
    bugs_caught:
      - "None == False is False"
      - "None is falsy but != False"
    safe_for_automation: true

  # Empty containers
  empty_list_falsy:
    value: "[]"
    bool_value: "False"
    bugs_caught:
      - "Empty list is falsy"
    safe_for_automation: true

  empty_dict_falsy:
    value: "{}"
    bool_value: "False"
    bugs_caught:
      - "Empty dict is falsy"
    safe_for_automation: true

  empty_string_falsy:
    value: "''"
    bool_value: "False"
    bugs_caught:
      - "Empty string is falsy"
    safe_for_automation: true

  zero_falsy:
    value: "0"
    bool_value: "False"
    bugs_caught:
      - "Zero is falsy"
    safe_for_automation: true

  # Mutable default arguments
  mutable_default:
    code: |
      def append_to(item, lst=[]):
          lst.append(item)
          return lst
    issue: "Default list shared between calls"
    bugs_caught:
      - "Mutable default argument"
      - "State accumulation between calls"
    safe_for_automation: true

  # Integer caching
  integer_identity:
    comparisons:
      - expr: "256 is 256"
        result: "True"
      - expr: "257 is 257"
        result: "False or True"
    bugs_caught:
      - "Integer caching -5 to 256"
      - "is vs == for numbers"
    safe_for_automation: true
    note: "Result varies by context in Python 3.8+"

  string_interning:
    comparisons:
      - expr: "'hello' is 'hello'"
        result: "True"
      - expr: "'hello world' is 'hello world'"
        result: "False or True"
    bugs_caught:
      - "String interning"
      - "is vs == for strings"
    safe_for_automation: true

  # Division
  floor_division:
    expressions:
      - expr: "7 // 2"
        result: 3
      - expr: "-7 // 2"
        result: -4
    bugs_caught:
      - "Floor division with negatives"
    safe_for_automation: true

  # Chained comparisons
  chained_comparison:
    expressions:
      - expr: "1 < 2 < 3"
        result: "True"
      - expr: "1 < 2 > 0"
        result: "True"
    bugs_caught:
      - "Chained comparison evaluation"
    safe_for_automation: true

  # List comprehension scope
  list_comp_scope:
    code: |
      x = 10
      [x for x in range(5)]
      print(x)  # What is x?
    issue: "List comp variable scope"
    bugs_caught:
      - "Loop variable scope in comprehension"
    safe_for_automation: true
    note: "Python 3: x is still 10. Python 2: x is 4"

  # Late binding closures
  closure_late_binding:
    code: |
      funcs = [lambda: i for i in range(3)]
      [f() for f in funcs]
    result: "[2, 2, 2]"
    bugs_caught:
      - "Late binding in closures"
      - "All lambdas return same value"
    safe_for_automation: true

  # Exception handling
  exception_in_finally:
    code: |
      def f():
          try:
              return 1
          finally:
              return 2
    result: "returns 2"
    bugs_caught:
      - "finally overrides return"
    safe_for_automation: true

  # Dictionary iteration
  dict_modification:
    code: |
      d = {'a': 1, 'b': 2}
      for k in d:
          del d[k]
    issue: "RuntimeError: dictionary changed size"
    bugs_caught:
      - "Dict modification during iteration"
    safe_for_automation: true

  # Unicode
  unicode_length:
    expressions:
      - expr: "len('😀')"
        result: 1
      - expr: "len('👨‍👩‍👧‍👦')"
        result: 7
    bugs_caught:
      - "Emoji length counting"
      - "ZWJ sequence handling"
    safe_for_automation: true