List Functions

The append() function is used to add an item to the end of the list:

nums = [1, 2, 3]
nums.append(4)
print(nums)

[1, 2, 3, 4]

insert() inserts a new item at the given position in the list:

words = ["Python", "fun"]
words.insert(1, "is")
print(words)

['Python', 'is', 'fun']

index() finds the first occurrence of a list item and returns its index.

letters = ['p', 'q', 'r', 's', 'p', 'u']
print(letters.index('r'))
print(letters.index('p'))
print(letters.index('q'))

2
0
1

list.count(item): Returns a count of how many times an item occurs in a list.

list.remove(item): Removes an item from a list.

list.reverse(): Reverses items in a list.

x = [2, 4, 6, 2, 7, 2, 9]
print(x.count(2))

x.remove(4)
print(x)

x.reverse()
print(x)

3
[2, 6, 2, 7, 2, 9]
[9, 2, 7, 2, 6, 2]

String Formatting

Strings have a format() function, which enables values to be embedded in it, using placeholders.

nums = [4, 5, 6]
msg = "Numbers: {0} {1} {2}". format(nums[0], nums[1], nums[2])
print(msg)

Numbers: 4 5 6

You can also name the placeholders, instead of the index numbers.

a = "{x}, {y}".format(x=5, y=12)
print(a)

5, 12

join() joins a list of strings with another string as a separator.

x = ", ".join(["spam", "eggs", "ham"])
print(x)
#prints "spam, eggs, ham"

spam, eggs, ham

split() is the opposite of join(). It turns a string with a certain separator into a list.

str = "some text goes here"
x = str.split(' ')
print(x)

['some', 'text', 'goes', 'here']

replace() replaces one substring in a string with another.

x = "Hello ME"
print(x.replace("ME", "world"))

Hello world

lower() and upper() change the case of a string to lowercase and uppercase.

print("This is a sentence.".upper())

print("AN ALL CAPS SENTENCE".lower())

THIS IS A SENTENCE.
an all caps sentence

Remember, strings are also lists. What is the output of this code?

txt = "hello"

print(max(txt))

=> o

You can create your own functions by using the def statement.

Here’s an example of a function named my_func. It takes no arguments, and prints "spam" three times.

def my_func():
  print("spam")
  print("spam")
  print("spam")

Functions can take arguments, which can be used to generate the function output.

def exclamation(word):
  print(word + "!")

exclamation("spam")

spam!