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This module is one in a collection of modules on Python designed for teaching ITSE 1359 Introduction to Scripting Languages: Python at Austin Community College in Austin, TX.
You were introduced to decision logic in the earlier module titled Itse 1359-1210-The While Loop . In that module I told you that Python supports a stand-alone decision capability, the if statement, which would be discussed in a future module. This is that future module.
You learned about the relational and logical operators that are used in decision logic in the module titled Itse1359-1220-Operators .
In this module, you will learn about
I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figuresand the Listings while you are reading about them.
(Note to blind and visually impaired students: Most of the Figures and all of the Listings inthis module are presented in plain text format and should be accessible using an audio screen reader or a braille display. Note however that the requiredindentation may not be properly represented by an audio screen reader.)
The pseudo-code for a Python if statement is shown in Figure 1 .
| Figure 1 . Pseudo-code for an if statement. |
|---|
if expression is True:
Execute one or more statements at same indentation levelExecute next statement |
The expression must be one that will evaluate to either True or False.
If the expression evaluates to True, the indented statement(s) that follow the colon will be executed in sequence.
If the expression evaluates to False, those indented statements will be skipped and the next statement following the if statement will be executed.
Listing 1 shows an example of the use of an if statement.
| Listing 1 . Example of if statement usage. |
|---|
# Illustrates the if statement
##-------------------------------
dogs = ["Affenpinscher","Afgan Hound","Akita"]if len(dogs)>2:
print(dogs[0])
print(dogs[1])
print(dogs[2])
print("Length of dogs list = " + str(len(dogs)))if len(dogs) == 2:
print(dogs[0])
print(dogs[1])
print(dogs[2])print(dogs) |
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