3 Control Statements and Program Development

Objectives

In this chapter you’ll:

• Decide whether to execute actions with the statements if, if …else and if …elif …else.

• Execute statements repeatedly with while and for.

• Shorten assignment expressions with augmented assignments.

• Use the for statement and the built-in range function to repeat actions for a sequence of values.

• Perform sentinel-controlled repetition with while.

• Learn problem-solving skills: understanding problem requirements, dividing problems into smaller pieces, developing algorithms to solve problems and implementing those algorithms in code.

• Develop algorithms through the process of top-down, stepwise refinement.

• Create compound conditions with the Boolean operators and, or and not.

• Stop looping with break.

• Force the next iteration of a loop with continue.

• Use some functional-style programming features to write scripts that are more concise, clearer, easier to debug and easier to parallelize.

Outline

1. 3.1 Introduction

2. 3.2 Algorithms

3. 3.3 Pseudocode

4. 3.4 Control Statements

5. 3.5 if Statement

6. 3.6 if…else and if…elif…else Statements

7. 3.7 while Statement

8. 3.8 for Statement

   1. 3.8.1 Iterables, Lists and Iterators

   2. 3.8.2 Built-In range Function

9. 3.9 Augmented Assignments

10. 3.10 Program Development: Sequence-Controlled Repetition

    1. 3.10.1 Requirements Statement

    2. 3.10.2 Pseudocode for the Algorithm

    3. 3.10.3 Coding the Algorithm in Python

    4. 3.10.4 Introduction to Formatted Strings

11. 3.11 Program Development: Sentinel-Controlled Repetition

12. 3.12 Program Development: Nested Control Statements

13. 3.13 Built-In Function range: A Deeper Look

14. 3.14 Using Type Decimal for Monetary Amounts

15. 3.15 break and continue Statements

16. 3.16 Boolean Operators and, or and not

17. 3.17 Intro to Data Science: Measures of Central Tendency—Mean, Median and Mode

18. 3.18 Wrap-Up

1. Exercises