Python Cheatsheet

The .count() function will count how many times a certain value appears within a string.

  sentence = input("Enter your sentence: ")
  e_count = sentence.count("e")
  print("There are", e_count, "e's!")

          

Enter your sentence: Hello there

There are 3 e's!

There are some golden rules when assigning

1. Variable names cannot take the name of a python reserved keyword such as print
2. The name goes on the left ⬅ & the value goes on the right ➡
3. Just use 1 =. Remember that == is a comparative operator.
4. Variable names cannot have spaces.

score = 0
name = "codefez"
                        

if you assign a value to a variable name that already exists, you will simply re-assign the original variable a new value.
This will result in losing the value that was originally held.

score = 0
print(score)

score = 1
print(score)
                        

0

1

Assigning variables can take up several lines! We can reduce the amount of required lines by assigning multiple variables on one line.

name, age, wears_glasses = "Joshua", 23, True
print(name, age, wears_glasses)
                            
                        

Joshua 23 True

a for loop allows us to iterate a list of instructions for a specified number of times.

for i in range(3):
    print("hi")
                

                  
    hi
    hi
    hi
                    

for number in range(3):
    print(number)
                    

  0
    1
    2
                        

an inline for loop allows us to iterate a list of instructions for a specified number of times on 1 line.

names = ["Alice", "Bob", "Charlie"]
upper_case = [name.upper() for name in names]
print(upper_case)
                

                  
    ALICE
    BOB
    CHARLIE
                    

The len() evaluates how big an object is.

In this case of a string, this is how many characters.

text = "fez"
len_of_text = len(text)
print(len_of_text)
                        

3

In the case of a list, it is how many elements there are in the list.

myList = ["fez", "code"]
len_of_list = len(myList)
print(len_of_list)
                        

2

The range() function is often used in a for loop.
It specifies between which number of times the for instructions should repeat.

for i in range(3):
    print(i)
                    

                        
    0
    1
    2

                    

for i in range(5,8):
    print(i)
                    

                        
    5
    6
    7
                        
                    

The input() function can also be used to collect user responses as either integers or numbers with decimals.

once the input is collected from the user, it is then cast into either an integer or a float (a number with decimals).

# This is an input for whole number (integer)
age = int(input("Enter your age"))

# This is an input for a floating point
# number (with decimals)
shoe_size = float(input("Enter your shoe size"))
                        

Enter your age

14

Enter your shoe size

8.5

The input() function pauses when executing the line of code for the user to enter an input.

The input must be stored in a variable.

age = input("How old are you?\n>")
                        

How old are you?
                        

The in operator checks if a character from a string or an element is in a list.

items = ["carrot","tomato","lettuce"]
if "tomato" in items:
    print("List includes fruit")
else:
    print("No fruit in list")
                        

List includes fruit

The not in operators checks if a character from a string or an element is NOT in a list.

items = ["carrot","tomato","lettuce"]
if "tomato" not in items:
    print("No fruit in list")
else:
    print("fruit in list")
                        

fruit in list

The if function selects code for execution if a condition is met. If it is not met, the instruction nested under the else block is executed.

x = 10

if x > 5:
    print("x is greater than 5")
else:
    print("x is less than or equal to 5")
                        

x is greater than 5
                        

The elif operand will execute the block of code if a given condition is met and doesn't meet the first condition.

x = 2

if x > 5:
    print("x is greater than 5")
elif x > 2:
    print("x is greater than or equal to 2")
else:
    print("x is less than 2")

            

x is greater than or equal to 2

Ternary operators allow you to execute an if/else statement on one line.

  x = int(input(" "))
  print(f"{x} is equal to 4.") if x==4 else print(f"{x} is not equal to 4")

          

The # symbol creates a line that is ignored by Python. This is called a comment and can be used to describe the purpose of a block of code for clarity later.

# The line below asks for a user's age
age = int(input("What's your age?"))
                        

What's your age?
                        

Multiple comment lines can also be achieved by using either 3 single or 3 double quotes.

"""The line below asks 
for a user's age """
age = int(input("What's your age?"))

'''The line above asks 
for a user's age '''
                        

What's your age?
                        

The lower() function converts all alphanumeric characters into lowercase

name = "CodeFez"
print(name.lower())
                        

codefez
                        

The upper() function converts all alphanumeric characters into uppercase

name = "CodeFez"
print(name.upper())
                        

CODEFEZ