Python Lab 2: User Input and Conditionals
Python Lab 2: User Input and Conditionals
Get User Input
Python has a built-in function called input
that will prompt the user and give us back the result, which can be stored into a variable.
print("Please enter your full name") name = input() name = input("Please enter your full name: ")
Conditional Statements
Conditional logic using if statements represent different paths a program can take based on some type of comparison of input.
if name == "Mark Zuckerberg": print("You work at Facebook") elif name == "Jack Dorsey": print("You work at Twitter") elif name == "Sundar Pichai": print("You work at Google") else: print("Not enough data")
Truthy & Falsy
All conditional checks resolve to either True or False
x = 1 x is 1 # True x is 0 # False
We can call values that resolve to True as “truthy”, and values that resolve to False as “falsy”. Besides False, other things that are naturally falsy include: empty objects, empty strings, None and zero (0).
Comparison Operators
Consider we are comparing two variables, x and y. Ex. x > y
Operator | What it does |
---|---|
== | Truthy if x has the same value as y |
!= | Truthy if x does NOT have the same value as b |
> | Truthy if x is greater than y |
< | Truthy if x is less than y |
>= | Truthy if x is greater than or equal to y |
<= | Truthy if x is less than or equal to y |
Logical Operators
The following operators can be used to make Boolean Logic comparisons or statements:
Operator | What it does |
---|---|
and | Truthy if both x AND y are true |
or | Truthy if either x OR y are true |
not | Truthy if the opposite of x is true |
is vs. “==”
In Python, ==
and is
are very similar in functionality, but they are not the same.
x = 1 x == 1 # True x is 1 # True x = [1, 2, 3] # A list of numbers. y = [1, 2, 3] x == y # True x is y # False z = y y is z # True
Nested Conditionals
if
statement inside an if
statement
Scratchpad file
# = assignment # == compare # name = input("Please enter your name: ") # if name != "Mark Zuckerberg": # print("You don't belong to Facebook") # elif name == "Jack Dorsey": # print("You don't belong to Twitter") # elif name == "Sundar Pichai": # print("You don't belong to Google") # else: # print("Whatever!") # Operators # == equal to # != not equal to # > great than # < less than # >= greater than or equal to # <= less than or equal to # age = input("Please enter your age: ") # age = int(age) # if age >= 21: # print("You are allowed to drink") # elif age >= 65: # print("You get drinks for free") # else: # print("Sorry you can't drink!") # if items > 20: # print("Oh, you have a lot of stuff") # elif items < 10: # print("Too bad, you can buy more.") # else: # print("That's perfect") # Truthiness # Falsyness # logged_in = "someuser@gmail.com" # if logged_in: # print("You have logged in, see the content") # else: # print("Sorry, please login to check") # Logical Operations # and # or # not # age = input("Please enter your age: ") # age = int(age) # if age >= 21 and age < 65: # print("You are allowed to drink") # elif age >= 65: # print("You get drinks for free") # elif age >= 18 and age < 21: # print("You can enter but you cannot drink") # else: # print("Sorry you can't drink, you're too young!") # NAME # city = "mumbai" # if city == "mumbai" or city == "bangalore": # print("You live in a tier 1 city") # if city == "pune" or city == "jaipur": # print("You live in a tier 2 city") # if not city == "mumbai": # print("You are out of Mumbai") # and -> LHS and RHS TRUE # 0, None, "" -> Falsy values # # username = "mark@fb.com" # if not username: # print("Hello my friend") # else: # print("You are not welcome") # is vs == # == - it checks for the value. # is - checks whether it is the same thing in memory # Nested conditionals age = input("How old are you? ") if age: age = int(age) if age >= 21 and age < 65: print("You are allowed to drink") elif age >= 65: print("You get drinks for free") elif age >= 18 and age < 21: print("You can enter but you cannot drink") else: print("Sorry you can't drink, you're too young!") else: print("Please enter a valid age!")
# For loop # numbers = [100, 20, 2, 24, 45] # for number in numbers: # num = (number / 2) * 2.3 # print(f"The value of this number is {num}") # name = "Stephen" # for char in name: # print(char) # Iterable - range of numbers, strings, lists, dictionaries # my_time = 4 # for time in [1, 2, 3, 4]: # print("Happy Birthday!") # my_time = time # print(my_time) # for item in iterable_object: # do something # for num in 10: # print("Hello World") # range(20) -> 0 # range(10, 21) -> # range(0, 21, 2) # range(10, 1, -1) # range(start = 0, end, step = 1) # for time in range(0, 6): # print("JUMP") # rant = input("How many times do you want to scream? ") # rant = int(rant) # for i in range(0, -50, -1): # print("CLEAN YOUR ROOM!!!!") # if i == 5: # print("OKAY OKAY, I'll do it!") # 1 - 20 -> # odd - "Fizz is odd" # even - "Fizz is even" # 5, 16, print("FizzBuzz") # num % 2 != 0 (odd) # for num in range(1, 21): # if num == 5 or num == 16: # print(f"{num}: FizzBuzz") # elif num % 2 == 0: # print(f"{num}: Fizz is even") # elif num % 2 != 0: # print(f"{num}: Fizz is odd") # While loop # password = input("Please enter your secret password: ") # while password != "tesla1": # print("INCORRECT PASSWORD! GET LOST!") # password = input("Please enter the correct password: ") # print("CORRECT! Hello...") # num = 10 # i = 1 # while i <= num: # print(f"{i}: Hello World") # i = i + 1 # break statement # password = input("Please enter your secret password: ") # while password != "tesla1": # if password == "GODMODE": # break # print("INCORRECT PASSWORD! GET LOST!") # password = input("Please enter the correct password: ") # print("CORRECT! Hello...") # num = 30 # i = 1 # j = 1 # while i <= num: # if i == 10: # while j < 5: # print("Hello world!") # j += 1 # print(f"{i}: Hello World") # i = i + 1 # Exercise 1 # 0 : 20 # 0 : -30 # 30 : -30 # Exercise 2: Rock paper scissor # best out of three # player1_wins = 3 # player2_wins = 0 # winning_score = 3 # while player1_wins >= 3 or player2_wins >= 3: # print("Player1 wins") # player1_wins += 1 # # code............... # if player1_wins > player2_wins: # print("PLAYER 1 is the victor!") # else: # print("PLAYER 2 is the vector!") # Data Structures -> Data Types # int, strings, None, List, Dicts # data structure # list = [1, "hello", 3, 4, True, None, [1, 2, 3, 4], [1, 2, 3, 5.5555]] # shopping_cart = ["apples", "cucumbers", "phone"] # results = [ # ["One", "Metallica", 3.49, 1000000, "Song performed by metallica from the album, St. Anger", # "bucket3.aws.amazonaws.com/photo-gal/11134/32/thumbnail_32.png"] # ["Fade to black", "Metallica", 3.49, 1000000, "Song performed by metallica from the album, St. Anger", # "bucket3.aws.amazonaws.com/photo-gal/11134/32/thumbnail_32.png"] # ["Fade to black", "Metallica", 3.49, 1000000, "Song performed by metallica from the album, St. Anger", # "bucket3.aws.amazonaws.com/photo-gal/11134/32/thumbnail_32.png"] # ]