Variables are fine on their own, but you can’t do much with them by themselves. Add them? Subtract them? That’s fine, but since we want more, we get more: introducing functions and methods!

# A function to get the number of characters in a string
len("butterscotch") # output: 12

# A function to sort a list
sorted([5, 4, 2, 3, 1]) # output: [1, 2, 3, 4, 5]

# A method to capitalize a string
"butterscotch".upper() # output: BUTTERSCOTCH

# A method to replace some text with some other text
"123123123".replace("12", "X") # output: X3X3X3

What’s the difference between functions and methods? Functions wrap around the outside of your variable/data, while methods are at the end of the variable/data. It’s a really stupid and useless difference, but it’s true.

I want to do something: how do I know if I need a function or a method? Google! Methods are more or less functions that are just typed differently. To a degree there’s no rhyme or reason as to which is which.

Remember! Don’t forget the () or your functions and methods won’t work.

Common functions

Functions and methods for numbers

# Round to X decimals
round(3.14159, 2)

# Round up and down
# We need to bring in some external libraries - code someone else wrote that isn't automatically included in Python
import math

Functions and methods for strings

# Length of a string

# Replace content in a string
"yourstring".replace("your", "my")

# Change the case of a string
"Your String".upper()
"Your String".lower()
"Your String".title()
"Your String".swapcase()

# Count the number of something in a string
"Your String".count("r")

# Test if a string ends with something
"Your String".endswith("ng")

# Split into a list based on some character
"Your String".split(" ")

# Join a list into a string based on some character
" ".join(["Your", "String"])

# Reverse a string
"Your String".reverse()

Functions and methods for lists

# Length of a list
len([1, 2, 3, 4])

# Largest in a list
max([1, 2, 3, 4])

# Smallest in a list
min([1, 2, 3, 4])

# Sort a list
sorted([5, 4, 3, 2, 1])

# Add elements in a list together
sum([1, 2, 3, 4])

# Count the number of something in a list
[1, 4, 3, 2, 1].count(1)

# Join a list into a string based on some character
" ".join(["Your", "String"])

Functions and methods for dictionaries

data = { 'name': 'Smush', 'breed': 'cat', 'age': 7 }

# Get the keys from a dictionary

# Get the values from a dictionary