Design Structures and Branching

Name: Design Structures and Branching
Author: John Crabtree

Explore Boolean data, operators, and expressions in Python

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Course: On-Demand

Programming often involves conditional execution. And in Python, we do this with the if statement. We have if followed by a Boolean expression that must evaluate to true or false, a colon, and then one or more statements that will be executed if, and only if the expression evaluates to true. Now there are two Boolean values that are part of the Python language and they are capitalized. And the type of these is called Bool. It's a class and the only two valid values for any Boolean variable is true or false. So I can write a very simple if statement by using the true literal, and then following that expression with a colon. The colon means we're not finished yet. I have to have at least one statement inside of the body of the if and the ellipsis there reminds me that that must be indented. And I will just print, hi. And then if I hit Enter on the next line with an ellipsis that tells the interactive environment that I'm finished with that block of statements, because I can define one or more statements embedded inside the body of the if that will be executed conditionally. And as you can imagine, if I do the same thing with a literal value of false, I will not see my output. So let's take a look at a program. I have X defined as two, and then I asked the question, is X equal to two? And if it is, I will print this, but regardless I will always print that. So to prove it, I will set X equal to a different value and run this same program after I save it. And you'll see that only the statements that are indented are affected by the if statement. Now be very careful when you do your indention Python is very picky about indention and you can't indent with one extra space or one space less, and you can't use tabs versus spaces. You notice the I-beam is moving one space at a time. I have spaces there. And so this will be fine. Also be aware that this is comparison. I'm comparing the variable on the left to the literal on the right. It is not assignment. Some languages like the C programming language allow you to put an assignment statement in for the expression. Also be aware that in Python the parentheses around your expression is optional.

Beginner Provider : John Crabtree 5 Lessons · 17m in Arabic, German, English, Spanish, French, Portuguese, Chinese

Course Description

These lessons begin with a discussion of the Boolean data type in Python (bool) along with the valid literal values and their use in simple if statements. After two-way if/else statements are demonstrated, the equality and relational Boolean operators are presented with example code. Logical operators and expressions are demonstrated and then the lessons conclude with multi-way decision structures that involve the evaluation of a potentially unlimited number of Boolean expressions.

LEARNING OBJECTIVES:

What You'll Learn

Recognize the Boolean data type in Python and its valid literal values of True and False
Use simple if statements to make single decisions
Build two-way if/else decision structures in Python
Apply equality and relational Boolean operators in expressions
Combine conditions using logical (Boolean) operators and expressions
Construct multi-way decision structures with elif to evaluate many Boolean expressions

Key Takeaways

The Boolean data type in Python (bool) has the valid literal values True and False.
Simple if statements let a program execute code based on a single Boolean condition.
Two-way if/else statements choose between two paths, and equality and relational operators produce the Boolean results that drive them.
Logical operators let you build compound Boolean expressions from simpler conditions.
Multi-way decision structures using elif are needed to evaluate a potentially unlimited number of Boolean expressions.

Frequently Asked Questions

What topics does this course cover?

It covers the Boolean data type in Python (bool) and its True and False literals, simple if statements, two-way if/else statements, equality and relational Boolean operators, logical operators and expressions, and multi-way decision structures using elif.

What lessons are included?

The course includes five lessons: Simple Decisions, Two-way Decisions, Equality and Relational Operators, Boolean Operators and Expressions, and Multi-way Decisions.

What skills will I gain from this course?

You will build skills in Boolean expressions, Boolean search, Boolean networks, programming concepts, programming language design, and the Python programming language.

When are multi-way decision structures used?

Multi-way decision structures, which use the elif function, are needed when you must evaluate a potentially unlimited number of Boolean expressions.