beginners_python_cheat_sheet_pcc_if_while - Beginner's Python If Statements and While Loops

Oct 13, 2026

Upload by awa

Beginner's guide to Python if statements and while loops, explaining how to evaluate conditions with True/False and how programs can respond accordingly. Covers conditional tests including equality, inequality, case-insensitive comparisons via lower(), numerical comparisons, and multi-condition logic using and/or. Includes if, if-else, and if-elif-else patterns, plus list-based membership and empty-list checks. Demonstrates accepting user input with input(), converting with int()/float(), and using while loops with counters, quitting prompts, flags, and break for loop control.

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Beginner's Python If Statements and While Loops

What are if statements?

What are while loops?

Conditional Tests

If statements and branches

Conditional tests with lists

Accepting input

While loops and loop control

Beginner's Python Cheat SheetIf Statementsand While Loops What are if statements? What are while loops? Python's if statements allow you to examine the current state of a program and respond appropriately to that state. You can write a simple if statement that checks one condition, or you can create a complex series of statements that identify the exact conditions you're interested in. while loops run as long as certain conditions remain true. You can use while loops to let your programs run as long as your users want them to. Conditional Tests A conditional test is an expression that can be evaluated as true or false. Python uses the values True and False to decide whether the code in an if statement should be executed. Checking for equality A single equal sign assigns a value to a variable. A double equal sign checks whether two values are equal. If your conditional tests aren't doing what you expect them to, make sure you're not accidentally using a single equal sign. >>> car = 'bmw' >>> car == 'bmw'True >>> car = 'audi' >>> car == 'bmw'False Ignoring case when making a comparison >>> car = 'Audi' >>> car.lower() == 'audi'True Checking for inequality >>> topping = 'mushrooms'>>> topping != 'anchovies'True Numerical comparisons Testing numerical values is similar to testing string values. Testing equality and inequality >>> age = 18 >>> age == 18 True >>> age != 18 False Comparison operators >>> age = 19 >>> age < 21 True >>> age <= 21 True >>> age > 21 False >>> age >= 21 False Checking multiple conditions You can check multiple conditions at the same time. The and operator returns True if all the conditions listed are true. The or operator returns True if any condition is true. Using and to check multiple conditions >>> age_0 = 22 >>> age_1 = 18 >>> age_0 >= 21 and age_1 >= 21 False >>> age_1 = 23 >>> age_0 >= 21 and age_1 >= 21 True Using or to check multiple conditions >>> age_0 = 22 >>> age_1 = 18 >>> age_0 >= 21 or age_1 >= 21 True >>> age_0 = 18 >>> age_0 >= 21 or age_1 >= 21 False Boolean values A boolean value is either True or False. Variables with boolean values are often used to keep track of certain conditions within a program. Simple boolean values game_active = True is_valid = True can_edit = False If statements Several kinds of if statements exist. Your choice of which to use depends on the number of conditions you need to test. You can have as many elif blocks as you need, and the else block is always optional. Simple if statement age = 19 if age >= 18: print("You're old enough to vote!") If-else statements age = 17 if age >= 18: print("You're old enough to vote!") else: print("You can't vote yet.") The if-elif-else chain age = 12 if age < 4: price = 0 elif age < 18: price = 25 else: price = 40 print(f"Your cost is ${price}.") Conditional tests with lists You can easily test whether a certain value is in a list. You can also test whether a list is empty before trying to loop through the list. Testing if a value is in a list >>> players = ['al', 'bea', 'cyn', 'dale']>>> 'al' in players True >>> 'eric' in players False Testing if two values are in a list >>> 'al' in players and 'cyn' in players Python Crash Course A Hands-on, Project-Based Introduction to Programming [ehmatthes.github.io/pcc_3e](ehmatthes.github.io/pcc_3e) Conditional tests with lists (cont. ) Testing if a value is not in a list banned_users = ['ann', 'chad', 'dee'] user = 'erin' if user not in banned_users: print("You can play!") Checking if a list is empty An empty list evaluates as False in an if statement. players = [] if players: for player in players: print(f"Player: {player.title()}") else: print("We have no players yet!") Accepting input You can allow your users to enter input using the input() function. All input is initially stored as a string. If you want to accept numerical input, you'll

FAQs

How do Python if statements decide whether code runs?

Python if statements evaluate conditional tests that result in True or False, and execute the associated block only when the result is True.

What is the difference between a single equal sign and a double equal sign in conditional tests?

A single equal sign assigns a value to a variable, while a double equal sign checks whether two values are equal.

How can a while loop run until the user chooses to quit?

Use a loop that continues while an entered message is not 'quit', updating the message each iteration with input() and printing it only when it isn’t 'quit'.

Oct 13, 2026

Upload by awa