3 Control Flow Free Online FlashCards

How does Python identify code blocks?

Python uses indentation to identify which statements belong to an `if`, `while`, or `for` block. Statements in the same block must be indented consistently.

What do Python's `and`, `or`, and `not` operators do?

`and` is true when both operands are true; `or` is true when at least one operand is true; `not` reverses a truth value.

What is short-circuit evaluation?

Short-circuit evaluation stops `and` when its left operand is false and stops `or` when its left operand is true, so unnecessary or unsafe expressions may not run.

Which common Python values are falsy?

Falsy values include `False`, `None`, numeric zero, and empty strings or collections. Most other objects are truthy.

When should Python use `==` rather than `is`?

Use `==` to compare values. Use `is` mainly for object identity checks involving singletons such as `None`.

What does `0 <= score <= 100` mean?

A chained comparison such as `0 <= score <= 100` expresses both comparisons and evaluates the middle expression only once.

How does Python choose among `if` and `elif` branches?

Python tests `if` and `elif` conditions from top to bottom and executes only the first matching branch. Remaining branches are skipped.

When does a `while` loop execute its body?

A `while` loop checks its condition before every iteration. If the condition is initially false, its body runs zero times.

When is a `while` loop appropriate?

Use a `while` loop when repetition depends on a condition that changes during execution or when the number of repetitions is not known in advance.

How does a Python `for` loop traverse data?

A `for` loop assigns each item from an iterable to a loop variable and runs its body. It ends when the iterable is exhausted.

How can a `for` loop obtain both index and item?

`enumerate()` supplies both an index and an item, as in `for index, name in enumerate(names):`.

Is the stop value included in `range()`?

The `stop` value in `range()` is exclusive. For example, `range(5)` produces the integers 0 through 4.