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  • units
    • Unit 4B: User Interfaces and Experiences (Bonus Material)
    • Unit 5b: Databases and Datastores
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    • Unit 7b: Processing Data from the Internet (Bonus Material)
    • Unit 9: Software Products and Services
    • Unit 8: Software Maintenance and Quality Control
    • Unit 7: Processing Data from the Internet
    • Unit 6: Data Visualization
    • Unit 5: Processing CSV Data
    • Unit 4: User Interfaces and Experiences
    • Unit 3: Python Datatypes
    • Unit 12: Project Presentations
    • Unit 2: Python Language Overview
    • Unit 11: Project Implementation Sprint
    • Unit 1: The Python Development Environment
    • Unit 10: Software Planning, Analysis, and Design
    • Unit 0: Onboarding
    • Unit 5B: Advanced Data Analytics
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  • Reference
  • If Statements
  • Case Statements

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Control Flow

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Last updated 5 years ago

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Reference

If Statements

Reference:

Use "If" statements to handle conditional logic (i.e. checking whether or not something is true and responding accordingly).

In Python, an "If" statement is defined using the if keyword, followed by a condition to be evaluated, followed by a colon (:), followed by one or more indented lines which contain statement(s) to be executed if the condition is met.

if True:
    print("YES THIS IS TRUE")

#> YES THIS IS TRUE

if 1 == 1:
    print("YES THIS IS TRUE")

#> YES THIS IS TRUE

if False:
    print("YES THIS IS TRUE")

if 1 == 2:
    print("YES THIS IS TRUE")

An "If" statement may include an else keyword, followed by a colon (:), followed by one or more indented lines which contain statement(s) to be executed if the original condition is not met.

if 1 == 2:
    print("YES THIS IS TRUE")
else:
    print("NO THIS IS FALSE")

#> NO THIS IS FALSE

An "If" statement, regardless of whether or not it contains an else keyword, can contain any number of elif keywords, each followed by a colon (:), followed by one or more indented lines which contain statement(s) to be executed if the condition is met. If there is an else keyword, it should come last.

# run this script a few times in a row...
import random

fruit = random.choice(["Apple", "Banana", "Orange"])

if fruit == "Orange":
    print("WE GOT AN ORANGE HERE")
elif fruit == "Banana":
    print("WE GOT A BANANA HERE")
elif fruit == "Peach":
    print("WE GOT A PEACH HERE")
else:
    print("NOT SURE WHAT WE GOT HERE")

As in other languages, statement order matters:

if True:
    print("First")
elif True:
    print("Second")

#> "First"

Case Statements

Python doesn't have "Case" statements. Try to use an "If" statement or a dictionary to accomplish what you are trying to do.

https://docs.python.org/3/tutorial/controlflow.html#if-statements
https://docs.python.org/3/tutorial/controlflow.html#for-statements
https://docs.python.org/3/tutorial/controlflow.html#break-and-continue-statements-and-else-clauses-on-loops
https://docs.python.org/3/tutorial/controlflow.html#pass-statements
https://docs.python.org/3/tutorial/controlflow.html#if-statements