Python Cheatsheet

Comparison Operators

These operators can be used during a comparison e.g. when implementing selection.

Comments

1
2

# This is a comment on a whole line
a = "Hi"  # This is a comment at the end of a line

Variables

Variables allow a value to be stored in memory. Python does not require a specific type to be defined during declaration.

1
2

a = "I am a string!"
count = 4

Output

Displaying a message in the terminal can be handled via the “print” method.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11

# Output by passing by value
print("Hello World!")

# Output by passing a single argument
message = "Hi"
print(message)

# Output by passing multiple arguments
a = "Hello"
b = "World!"
print(a, b)

Input

Input from the user can be captured via the “input” method.

1
2
3
4
5

# Ask for user input with a message
name = input("Enter Your Name: ")

# Ask for user input with no message
name = input()

Selection

Selection is handled in Python using “if statements”.

• Only the first expression that is TRUE will execute
• There must be at least an “if” statement to include “elif” or “else”
• “elif” statements can allow for multiple selections
• “else” does not require a expression, it will only run when all other expressions are FALSE
• “elif” expressions can only be after an “if”
• An “else” statement can only be added at the end

1
2
3
4
5
6

if <comparision>:
    ...
elif <comparision>:
    ...
else:
    ...

Example Program:

1
2
3
4
5
6
7
8

name = "Steve"

if name == "Leo":
    ...
elif len(name) == 3:
    ...
else:
    ...

Iteration

For

A for loop allows to iterate over a sequence of values.

1
2
3
4
5
6
7
8
9

message = "Welcome"

# Iterate using range
for i in range(len(message)):
    print(i)

# Iterate over items
for character in message:
    print(character)

While

A while loop allows for a condition to be checked before each iteration.

1
2
3
4
5
6

message = "Welcome"

i = 0
while i != len(message):
    print(i)
    i = i + 1