# Chapter 13 - Summary¶

Chapter 13 included the following concepts from computing.

• Boolean Expression - A Boolean expression is one that is either true or false. This is also called a logical expression.
• Condition - A condition is something that is either true or false. This is also called a Boolean expression or a logical expression.
• Conditional Execution - Conditional execution means that one or more statements are executed only when a condition (logical expression) is true. This is also called a conditional. The statements that are executed when the condition is true are called the body.
• Decision - A decision is a choice between at least two choices.
• Input - The `input` function returns a value that the user enters.
• Logical Expression - A logical expression is one that is either true or false, like `x == 3`. This is also called a Boolean expression.

## Summary of Python Keywords and Functions¶

• And - The keyword `and` is used to join two logical expressions and then both of the logical expressions must be true for the joined expression to be true.
• Else - The keyword `else` is used to execute one or more statements in a block following the `else` when the condition in the `if` part of the statement is false. An `else` must always have an `if` statement before it.
• Elif - The keyword `elif` is used when you want to have a conditional with 3 or more possibile options. Add as many `elif` statements as you need after an `if` and before a `else`.
• If - The Python keyword `if` is used to start a condition. It is followed by a Boolean expression and then has one or more statements in the body of the loop that are executed only if the Boolean expression is true.
• Not - The keyword `not` is used to negate a logical expression. If the original expression is true the negated expression is false and if the original expression is false the negated expression is true.
• Str - The function `str` turns a number into a string so that it can be appended to a string.

Note

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Next Section - Chapter 13 Exercises