Jupyter Notebook Cheat Sheets

Quick reference notes for students: variables, lists, dictionaries, conditionals, loops, functions and libraries.

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Quick reference

Cheat Sheet Index

Use this index to jump directly to the Python topic you need.

1VariablesJupyter Notebook 1 2Lists, including DictionariesJupyter Notebook 2 3ConditionalsJupyter Notebook 3 4LoopsJupyter Notebook 4 5Functions & LibrariesJupyter Notebook 5
1

Jupyter Notebook 1

Variables

print("...")

Prints an output defined by the user. It can also be used to print out variables.

print("Hello world")
>> Hello world

name = "Alvin"
print("Hello", name, "how are you?")
>> Hello Alvin how are you?

input("...")

Inputs can be used to save a variable typed in by the user.

name = str(input("What is your name?"))
>> What is your name? Kate

print("Hello", name)
>> Hello Kate

int(...)

Tells Python an input is an integer.

saved_num = int(input("Write your favourite number"))
>> Write your favourite number 42

float(...)

Tells Python an input is a float.

saved_num_2 = float(input("Write your favourite number"))
>> Write your favourite number 42.1

str(...)

Tells Python the input is a string.

name = str(input("What is your name?"))
>> What is your name? Franziska

len(...)

Returns the length of a string.

name = "Samuel"
print(len(name))
>> 6
2

Jupyter Notebook 2

Lists & Dictionaries

Dictionaries

Dictionaries are special lists. They are defined using curly brackets { ... }. You can access them using keys instead of indexes, which sometimes makes programming easier. Dictionaries are marked using { key : object } as follows:

favourite_things = {"food" : "sushi", "number" : 42, "language" : "French"}
print(favourite_things["language"])
>> "French"

list.append(...)

Adds an element to a list.

playlist = ["Believer", "Fireflies"]
playlist.append("Radioactive")
print(playlist)
>> "Believer", "Fireflies", "Radioactive"

list.pop(...)

Removes an element from a list.

playlist = ["Believer", "Fireflies", "Radioactive"]
playlist.pop(0)
>> "Fireflies", "Radioactive"

list[n]

Access the nth element of the list.

playlist = ["Believer", "Fireflies", "Radioactive"]
print(playlist[2])
>> "Radioactive"

print(playlist[0])
>> "Believer"

list[n] = ...

Replaces the nth element of the list.

playlist = ["Believer", "Fireflies", "Radioactive"]
playlist[2] = "My Life"
print(playlist)
>> "Believer", "Fireflies", "My Life"

in

Checks if an element is in a list.

playlist = ["Believer", "Fireflies", "Radioactive"]
print("Fireflies" in playlist)
>> True

string[...]

Strings are also lists.

name = "Emma"
print(name[3])
>> "a"
3

Jupyter Notebook 3

Conditionals

if (...):

Runs the indented code if the condition is fulfilled.

current_temperature = 240
target_temperature = 220

if current_temperature > target_temperature:
    print("The oven is too warm, let it cool down a bit.")

>> "The oven is too warm, let it cool down a bit."

elif (...):

Runs the indented code only if the condition before it is not fulfilled and its own condition is fulfilled.

current_temperature = 240
target_temperature = 260

if current_temperature > target_temperature:
    print("The oven is too warm, let it cool down a bit.")
elif current_temperature < target_temperature:
    print("The oven is too cold, let it warm up a bit.")

>> "The oven is too cold, let it warm up a bit."

else:

Runs the indented code only if all the conditions before it failed.

current_temperature = 240
target_temperature = 240

if current_temperature > target_temperature:
    print("The oven is too warm, let it cool down a bit.")
elif current_temperature < target_temperature:
    print("The oven is too cold, let it warm up a bit.")
else:
    print("The oven is ready.")

>> "The oven is ready."

len(...)

Calculates the length of a string or list.

playlist = ["One Day", "Next to Me", "Tri Poloski"]

if len(playlist) > 10:
    print("This is a long playlist")
else:
    print("This playlist is short.")

>> "This playlist is short."
4

Jupyter Notebook 4

Loops

There is a jump in difficulty between the last Jupyter notebook and this Jupyter Notebook. It is normal that the exercises take more time to solve. If you are stuck, ask your instructors. They are here to help.

range(n)

Creates a list going from 0 to n-1.

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

>> 0, 1, 2

range(start, stop, step)

Creates a list starting at “start”, stopping at “stop - 1” and going by “step”.

for k in range(1, 5, 1):
    print(k, "repeat")

>> 1 repeat, 2 repeat, 3 repeat, 4 repeat

for a in range(3): for b in range(2): print(a,":", b)

Nested loops.

for a in range(3):
    for b in range(2):
        print(a, ":", b)

>> 0 : 0
>> 0 : 1
>> 1 : 0
>> 1 : 1
>> 2 : 0
>> 2 : 1

number % n

Takes the nth modulo of the number.

print(23 % 5)
>> 3

number // n

Performs the whole division of the number through n.

print(23 // 5)
>> 4

print(4 * 5 + 23 % 5)
>> 23

list.split()

Splits a list at every space character.

text = "hello world"
for i in text.split():
    print(i)

>> hello
>> world
5

Jupyter Notebook 5

Functions & Libraries

from ... import ...

Imports a specific function from a library.

from math import sqrt
print(sqrt(4))
>> 2

import ... as ...

Imports a whole library as a string. Requires special syntax when calling functions.

import math as mt
print(mt.sqrt(4))
>> 2

from ... import *

Imports a whole library. Does not require specific syntax.

from math import *
print(sqrt(4))
>> 2

def ... (a, b):
    _____
    _____
    return(c)

Defines a function manually with arguments a and b, and returns c.

def addition(a, b):
    sum = a + b
    return(sum)

print( addition( 8, -6) )
>> 2