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Python Flashcards: Fundamentals

Python — Fundamentals Flashcards

30 interactive flashcards covering core Python concepts from types and control flow to metaclasses and the GIL. Press Space to flip, rate 1-4.

Additional Flashcard Topics

  • List Comprehensions: [x**2 for x in range(10) if x % 2 == 0] — concise syntax for creating filtered lists. Nested comprehensions flatten to single expressions.

  • Generators: yield produces values lazily. Generators consume O(1) memory vs O(n) for lists. generator_expression syntax: (x**2 for x in range(10)).

  • Decorators: functions that modify other functions. @decorator syntax. functools.wraps preserves the original function’s metadata.

  • Context Managers: with open('file') as f: ensures cleanup. Implement via __enter__/__exit__ or contextlib.contextmanager.

  • Magic Methods: __init__, __str__, __repr__, __getitem__, __len__. They define how objects behave with built-in operations.

Intuition

Python is a dynamically typed, interpreted language where everything is an object — including functions, classes, and modules. List comprehensions provide concise syntax for creating lists from iterables, and generators yield values lazily (one at a time) instead of building entire lists in memory. The GIL (Global Interpreter Lock) ensures only one thread executes Python bytecode at a time, simplifying memory management but limiting CPU-bound parallelism. Python’s “batteries included” standard library is one of its greatest strengths.

Common Pitfalls

  • Mutable default arguments: Defining def f(x=[]) — the default list is shared across all calls, so mutations persist. Use None as the default and create a new list inside the function.
  • Shallow vs deep copy: list.copy() or list() creates a shallow copy — nested objects are still shared. Use copy.deepcopy() for independent copies of nested structures.
  • Late binding closures: Closures in loops capture the variable by reference, not by value — the loop variable changes before the closure executes, producing unexpected results. Use a default argument to capture the current value.
  • GIL limitations: The GIL prevents true parallelism for CPU-bound threads. Use multiprocessing for CPU-bound work, threading for I/O-bound work.
  • Name mangling: __name in a class becomes _ClassName__name externally. This is not true privacy — it’s name mangling to avoid naming conflicts.

Cross-References