# Chapter 15 - Concept Summary¶

Chapter 15 included the following concepts from computing.

• 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 of the loop.

• Decision - A decision is a choice between at least two choices.

• Edge Detection - Edge detection is a image processing technique. It finds the “edges” in an image which are the areas of high constrast or where the color changes.

• Posterize - Posterize means to reduce the number of colors in an image so that it looks like a poster.

## 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.

Note

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