Lists¶

A list is a Python data type representing a sequence of elements. You can have lists of strings:

names = ['Hannah', 'Emily', 'Madison', 'Ashley', 'Sarah']

and also lists of numbers:

numbers = [25952, 23073, 19967, 17994, 17687]

Accessing elements of lists¶

Using square brackets, any element of a list and tuple can be accessed. The first character has the index 0.

print(names[0])
print(numbers[3])

Negative indices start counting from the last character.

print(names[-1])

Lists can be sliced by applying square brackets in the same way as strings.

names = ['Hannah', 'Emily', 'Sarah', 'Maria']
names[1:3]
names[0:2]
names[:3]
names[-2:]

You can use slicing to create a copy:

girls = names[:]

Add a new element to the end of the list:

names.append('Marilyn')

Remove an element at a given index:

names.remove(3)

Remove the last element:

names.pop()

You can replace individual elements of a list by using an index in an assignment operation:

names[4] = 'Jessica'

names.sort()

The itemgetter module allows you to sort lists by a specific column. E.g. to sort names by the 3rd character:

from operator import itemgetter

cities.sort(key=itemgetter(2))

You can give a tuple of indices to sort first by one, then the other column:

cities.sort(key=itemgetter((1, 0)))

names = ['Hannah', 'Emily', 'Sarah', 'Emily', 'Maria']
names.count('Emily')