Python Fundamentals — Free Sample

A 5-question sample covering Python data structures, function semantics, list comprehension syntax, language guarantees, and generators. Items focus on conceptual understanding rather than code-tracing — that's reserved for the full 50-question assessment. For a verified Skills Passport credential, take the full assessment.

1. What's the result of multiplying a list by an integer in Python — for example, `[1, 2] * 3`?

Throws a TypeError because list and int can't be multiplied. Creates a new list with the elements repeated N times — `[1, 2, 1, 2, 1, 2]`. Adds N copies of each element to the existing list in place — `[1, 1, 1, 2, 2, 2]`. Multiplies each element by the integer — `[3, 6]`.

2. When is a mutable default argument (like `def f(items=[]):`) evaluated in Python?

Each time the function is called — a fresh list is created on every call. Once at function definition time; the same list object is reused on every subsequent call. Only the first time the function is called. Whenever the function is called without explicitly passing a value for that argument, a new default is created.

3. Which expression is a valid Python list comprehension that produces `[0, 4, 16]` from `range(5)`?

`[for x in range(5) if x % 2 == 0: x*x]` `[x*x for x in range(5) if x % 2 == 0]` `list(x*x where x in range(5) and x % 2 == 0)` `[x*x in range(5) where x % 2 == 0]`

4. In Python 3.7 and later, dictionaries maintain...

No guaranteed iteration order; the order is implementation-defined and may differ across runs. Insertion order, by language guarantee — keys are iterated in the order they were first inserted. Sorted order by key, lexicographically. Hash-bucket order, optimized for lookup speed but unpredictable to the user.

5. What does the `yield` keyword do inside a Python function?

Returns a value and exits the function permanently — equivalent to `return`. Produces a value, pauses the function's execution, and allows the caller to resume it for the next value. Synchronizes execution between threads, releasing the GIL temporarily. Logs the value to a generator log for later debugging.

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