>>>42==42True>>>40==42False>>>'hello'=='hello'True>>>'hello'=='Hello'False>>>'dog'!='cat'True>>>42==42.0True>>>42=='42'False

>>>(4<5)and(5<6)True>>>(4<5)and(9<6)False>>>(1==2)or(2==2)True

>>>2+2==4andnot2+2==5and2*2==2+2True>>># In the statement below 3 < 4 and 5 > 5 gets executed first evaluating to False>>># Then 5 > 4 returns True so the results after True or False is True>>>5>4or3<4and5>5True>>># Now the statement within parentheses gets executed first so True and False returns False.>>>(5>4or3<4)and5>5False

>>> name='Debora'>>>if name=='Debora':...print('Hi, Debora')...# Hi, Debora>>>if name!='George':...print('You are not George')...# You are not George

>>> name='Debora'>>>if name=='George':...print('Hi, George.')...else:...print('You are not George')...# You are not George

>>> name='George'>>>if name=='Debora':...print('Hi Debora!')...elif name=='George':...print('Hi George!')...# Hi George!

>>> name='Antony'>>>if name=='Debora':...print('Hi Debora!')...elif name=='George':...print('Hi George!')...else:...print('Who are you?')...# Who are you?

<expression1> if <condition> else <expression2>

>>> age=15>>># this if statement:>>>if age<18:...print('kid')...else:...print('adult')...# output: kid>>># is equivalent to this ternary operator:>>>print('kid'if age<18else'adult')# output: kid

>>> age=15>>># this ternary operator:>>>print('kid'if age<13else'teen'if age<18else'adult')>>># is equivalent to this if statement:>>>if age<13:...print('kid')...else:...if age<18:...print('teen')...else:...print('adult')...# output: teen

TheSwitch-Case statements, orStructural Pattern Matching, was firstly introduced in 2020 viaPEP 622, and then officially released withPython 3.10 in September 2022.

Matching single values

>>> response_code=201>>>match response_code:...case200:...print("OK")...case201:...print("Created")...case300:...print("Multiple Choices")...case307:...print("Temporary Redirect")...case404:...print("404 Not Found")...case500:...print("Internal Server Error")...case502:...print("502 Bad Gateway")...# Created

Matching with the or Pattern

In this example, the pipe character (| oror) allows python to return the same response for two or more cases.

>>> response_code=502>>>match response_code:...case200|201:...print("OK")...case300|307:...print("Redirect")...case400|401:...print("Bad Request")...case500|502:...print("Internal Server Error")...# Internal Server Error

Matching by the length of an Iterable

>>> today_responses=[200,300,404,500]>>>match today_responses:...case[a]:...print(f"One response today:{a}")...case[a, b]:...print(f"Two responses today:{a} and{b}")...case[a, b,*rest]:...print(f"All responses:{a},{b},{rest}")...# All responses: 200, 300, [404, 500]

Default value

The underscore symbol (_) is used to define a default case:

>>> response_code=800>>>match response_code:...case200|201:...print("OK")...case300|307:...print("Redirect")...case400|401:...print("Bad Request")...case500|502:...print("Internal Server Error")...case_:...print("Invalid Code")...# Invalid Code

Matching Builtin Classes

>>> response_code="300">>>match response_code:...caseint():...print('Code is a number')...casestr():...print('Code is a string')...case_:...print('Code is neither a string nor a number')...# Code is a string

Guarding Match-Case Statements

>>> response_code=300>>>match response_code:...caseint():...if response_code>99and response_code<500:...print('Code is a valid number')...case_:...print('Code is an invalid number')...# Code is a valid number

while Loop Statements

The while statement is used for repeated execution as long as an expression isTrue:

>>> spam=0>>>while spam<5:...print('Hello, world.')...     spam= spam+1...# Hello, world.# Hello, world.# Hello, world.# Hello, world.# Hello, world.

break Statements

If the execution reaches abreak statement, it immediately exits thewhile loop’s clause:

>>>whileTrue:...     name=input('Please type your name: ')...if name=='your name':...break...>>>print('Thank you!')# Please type your name: your name# Thank you!

continue Statements

When the program execution reaches acontinue statement, the program execution immediately jumps back to the start of the loop.

>>>whileTrue:...     name=input('Who are you? ')...if name!='Joe':...continue...     password=input('Password? (It is a fish.): ')...if password=='swordfish':...break...>>>print('Access granted.')# Who are you? Charles# Who are you? Debora# Who are you? Joe# Password? (It is a fish.): swordfish# Access granted.

For loop

Thefor loop iterates over alist,tuple,dictionary,set orstring:

>>> pets=['Bella','Milo','Loki']>>>for petin pets:...print(pet)...# Bella# Milo# Loki

The range() function

Therange() function returns a sequence of numbers. It starts from 0, increments by 1, and stops before a specified number:

>>>for iinrange(5):...print(f'Will stop at 5! or 4? ({i})')...# Will stop at 5! or 4? (0)# Will stop at 5! or 4? (1)# Will stop at 5! or 4? (2)# Will stop at 5! or 4? (3)# Will stop at 5! or 4? (4)

Therange() function can also modify its 3 defaults arguments. The first two will be thestart andstop values, and the third will be thestep argument. The step is the amount that the variable is increased by after each iteration.

# range(start, stop, step)>>>for iinrange(0,10,2):...print(i)...# 0# 2# 4# 6# 8

You can even use a negative number for the step argument to make the for loop count down instead of up.

>>>for iinrange(5,-1,-1):...print(i)...# 5# 4# 3# 2# 1# 0

For else statement

This allows to specify a statement to execute in case of the full loop has been executed. Only useful when abreak condition can occur in the loop:

>>>for iin[1,2,3,4,5]:...if i==3:...break...else:...print("only executed when no item is equal to 3")

Ending a Program with sys.exit()

exit() function allows exiting Python.

>>>import sys>>>whileTrue:...     feedback=input('Type exit to exit: ')...if feedback=='exit':...print(f'You typed{feedback}.')...         sys.exit()...# Type exit to exit: open# Type exit to exit: close# Type exit to exit: exit# You typed exit

Relevant links

• Basics
• Functions
• Exception Handling
• Lists and Tuples
• Sets
• Dictionaries
• Comprehensions

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