Python “Cheatsheet”

print()

Program output:

(blank line)

print('Hello, world!')
print(17)
print([5, 8, 13])

Program output:

Hello, world!
17
[5, 8, 13]

print('My first sentence.', end=' ')
print('My second sentence.')

Program output:

My first sentence. My second sentence.

name = input('What is your name? ')

• name is a variable that will save the input
• input() waits for the user to hit Enter, then returns everything typed before that
• 'What is your name? ' is a prompt for the user

Creates a temporary list of numbers

range(5)      # produces 0, 1, 2, 3, 4
range(6, 11)  # produces 6, 7, 8, 9, 10

age = 37
if age > 18:
    print('Please go vote!')

Program output:

Please go vote!

secretNumber = 17
guess = 23
if guess < secretNumber:
    print('Too low!')
elif guess > secretNumber:
    print('Too high!')

Program output:

Too high!

roll = random.randrange(1,7)
if roll == 1:
    print('Advance 1 space.')
elif roll < 5:
    print('Advance 2 spaces.')
else:
    print('Advance 1 space and roll again.')

Program output:
(assume randrange returned a 5)

Advance 1 space and roll again.

beat = 1
while beat <= 4:
    print(str(beat) + '-ee-and-uh')
    beat += 1

Program output:

1-ee-and-uh
2-ee-and-uh
3-ee-and-uh
4-ee-and-uh

In this loop, beat is the sentinel variable. Notice that beat was defined on the first line, was part of the looping condition, and got modified in the body of the loop. Those are all necessary features of a sentinel variable!

for letter in 'haberdashery':
    print(letter + '~', end='')

Program output:

h~a~b~e~r~d~a~s~h~e~r~y~

animals = ['zebra', 'yeti', 'X-ray fish', 'wildebeest', 'viper']
for animal in animals:
   print(animal[0].upper(), 'is for', animal)

Program output:

Z is for zebra
Y is for yeti
X is for X-ray fish
W is for wildebeest
V is for viper

for x in range(10):
    print(x**2, end=' ')

Program output:

0 1 4 9 16 25 36 49 64 81 

def interruptingFrog():
    print('rrribbit!')

The def tells Python that you are defining a new function named interruptingFrog(). The empty parentheses are important (and they won’t always be empty!). Anything indented below that def line will be considered part of the function.

interruptingFrog()

Program output:

rrribbit!

def multiply(n1, n2):
    product = n1 * n2
    print(product)

multiply(5, 7)

Program output:

35

• n1 and n2 are parameters
• when you call multiply, it requires two inputs

def getDirection():
    directions = ['N', 'S', 'E', 'W']
    direct = input('What direction do you want to go? ')
    while True:
        if direct not in directions:
            direct = input('Please enter N, S, E, or W: ')
        else:
            return direct

• return outputs to the program (invisible), where print outputs to the console (visible)
• return can break out of an otherwise infinite loop!

Defining a list:

soup = ['bean chili', 'clam chowder', 'French onion soup', 
        'butternut squash bisque']

Checking if a certain item is on a list:

print('gazpacho' in soup)

Program output:

False

Looping through a list:

for s in soup:
    print('Yum, a nice hot bowl of ' + s + '!')

Program output:

Yum, a nice hot bowl of bean chili!
Yum, a nice hot bowl of clam chowder!
Yum, a nice hot bowl of French onion soup!
Yum, a nice hot bowl of butternut squash bisque!

Indexing a list:

print(soup[1])

Program output:

clam chowder

(Remember that indexing starts at 0.)

Defining a dictionary:

MAwinter = {'October': 'cold and windy and rainy', 
            'November': 'cold and windy',
            'December': 'cold and hopefully snowy',
            'January': 'just cold',
            'February': 'extra cold and windy',
            'March': 'cold and snowy'}

Indexing a dictionary:

print(MAwinter['January'])

Program output:

just cold

(Use keys to access values.)

Checking if a certain item is in a dictionary:

mon = 'March'
if mon in MAwinter:
    print(MAwinter[mon])

Program output:

cold and snowy

Looping through a dictionary:

for month in MAwinter:
    print('In ' + month + ', the weather is ' + MAwinter[month] + '.')

Program output:

In October, the weather is cold and windy and rainy.
In November, the weather is cold and windy.
In December, the weather is cold and hopefully snowy.
In January, the weather is just cold.
In February, the weather is extra cold and windy.
In March, the weather is cold and snowy.