Comprehensions and Iterators Flashcards

Which syntax creates a list comprehension in Python?

Answer: [x for x in range(5)]

List comprehensions use square brackets: `[expression for item in iterable]`.

What does a generator expression return compared to a list comprehension?

Answer: A lazy iterator evaluated on demand

A generator expression (using parentheses) returns an iterator that yields values lazily, using less memory.

What is the result of `[x**2 for x in range(4)]`?

Answer: [0, 1, 4, 9]

`range(4)` produces 0,1,2,3 and squaring each gives [0, 1, 4, 9].

How do you add a condition to a list comprehension to include only even numbers?

Answer: [x for x in range(10) if x%2==0]

A conditional list comprehension uses `if condition` at the end: `[x for x in iterable if condition]`.

Which syntax creates a dictionary comprehension?

Answer: {k:v for k,v in items}

Dictionary comprehensions use `{key: value for ...}` syntax with curly braces and a colon.

What does the `enumerate()` function return when iterating?

Answer: A tuple of (index, value)

`enumerate()` yields `(index, value)` tuples for each item in the iterable.