Python flashcards, generated for you.

'==' compares values (content equality), while 'is' compares object identity (same memory address). Example: [1,2] == [1,2] is True, but [1,2] is [1,2] is False.

Mutable defaults (lists, dicts) are created once at function definition, not on each call. All calls share the same object. Use None and create a new object inside the function instead: def f(x=None): x = x or []

Negative indices count from the end: list[-1] is the last element, list[-2] is second-to-last. In slicing, list[start:stop:step], negative indices work the same way. list[:-1] excludes the last element.

append() adds a single element (or object) to the end. extend() iterates over an iterable and adds each element. Example: [1].append([2]) → [1, [2]]; [1].extend([2]) → [1, 2]

pass is a null operation—when executed, nothing happens. Used as a placeholder in functions, classes, loops, or conditionals where syntax requires a body but no code is needed yet.

LEGB is the order Python searches for variables: Local → Enclosing (nonlocal) → Global → Built-in. Python stops at the first match. Use 'nonlocal' or 'global' keywords to modify outer-scope variables inside a function.

Assignment (x = ...) creates a local variable, so referencing x before assignment raises UnboundLocalError. Mutating x[0] doesn't reassign x itself, so it accesses the global x. Use 'global x' to reassign a global variable.

'*args' captures positional arguments as a tuple; '**kwargs' captures keyword arguments as a dictionary. Example: def f(*args, **kwargs): print(args, kwargs); f(1, 2, a=3, b=4) → (1, 2) {'a': 3, 'b': 4}

'in' checks if a key exists in a dictionary, not the value. Example: 'a' in {'a': 1} is True, but 1 in {'a': 1} is False. Use 'value in dict.values()' to check for values.

'and' returns the first falsy value (or last value if all truthy); 'or' returns the first truthy value (or last if all falsy). They don't return bool—they return the actual object. Example: 0 or 'default' → 'default'; [] and 5 → []