Selection and loops in Python

Overview

if, elif and else, range() with worked values, for and while loops, iteration over lists and strings, nested loops, and single entry and exit points.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is the difference between initialisation and assignment?

   Model answer

   Initialisation gives a variable its first value, such as total = 0. Assignment is any statement that stores a value in a variable, including every later change.

2. 2

   Define a command sequence.

   Model answer

   A command sequence is a group of statements carried out one after another in order. Statements at the same indentation inside a block form a sequence.

3. 3

   What is printed when x = 7 runs through if x > 10: print("big"), then elif x > 5: print("medium"), then else: print("small")?

   Model answer

   The code prints medium. The first test is False, so the elif test x > 5 is checked and is True.

4. 4

   Why is if mark >= 40: grade = "C", followed by elif mark >= 70: grade = "A", a logic error?

   Model answer

   Python stops at the first True test, so a mark of 85 is given C. The highest boundary must be tested first.

5. 5

   List the values produced by range(5).

   Model answer

   The call range(5) produces 0, 1, 2, 3 and 4. The start defaults to 0 and the stop value 5 is not included.

6. 6

   List the values produced by range(2, 11, 3).

   Model answer

   The values are 2, 5 and 8. The next value would be 11, which is the stop value and is excluded.

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.