📝 Collections in Python#

Lists#

Lists are defined using [], items in a list are separated by ,.

Lists are used to store multiple items in a single variable.

Lists are ordered#

list1 = [1, 2, 3, 4]
list2 = [2, 3, 4, 1]

[1, 2, 3, 4] == [2, 3, 4, 1]

False

You can add a value to a list.

  • This can be done with the built-in method <obj>.append(<index>)

list1.append(5)

list1

[1, 2, 3, 4, 5]

You can remove items from a list

  • this can be done with the built-in method <obj>.pop(<index>)

list1.pop(2)

3

list1

[1, 2, 4, 5]

Lists Allow Duplications#

list1 = [1, 1, 1]

list1

[1, 1, 1]

Changing a value of a list#

Note

Python supports indexing of ordered objects using `[{index}]`, it is important to note that the index starts at 0.

Replacing a value

list1[0] = "Drexel"

list1

['Drexel', 1, 1]

Inserting a value

list1.insert(1, "Dragons")

list1

['Drexel', 'Dragons', 1, 1]

Sorting Lists#

list1 = [5, 2, 3, 1]

list1.sort()
list1

[1, 2, 3, 5]

list2 = ["Drexel", "Dragons"]
list2.sort()

list2

['Dragons', 'Drexel']

Lists can contain multiple data types#

list1 = ["Drexel", 1, 1.0]

print(type(list1[0]))
print(type(list1[1]))
print(type(list1[2]))

<class 'str'>
<class 'int'>
<class 'float'>

You can even store list of list

list2 = [list1, list1]
list2

[['Drexel', 1, 1.0], ['Drexel', 1, 1.0]]

or lists of lists of lists

list3 = [list2, list2]
list3

[[['Drexel', 1, 1.0], ['Drexel', 1, 1.0]],
 [['Drexel', 1, 1.0], ['Drexel', 1, 1.0]]]

You can get the length of a list using the method len()

print(len(list1))
print(len(list2))
print(len(list3))

3
2
2

Tuple#

A tuple is a collection that can store multiple ordered items that are unchangeable.

Syntax

Tuples are made using ({obj}, {obj}) 
thistuple = ("Drexel", "Dragons", list2)

print(thistuple)

('Drexel', 'Dragons', [['Drexel', 1, 1.0], ['Drexel', 1, 1.0]])

Usually tuples are used to move objects, which are then unpacked to be used.

statement = ("Drexel", "Dragons", "Football", 0)

(University, Mascot, Sport, losses) = statement

print(f"school: {University}")
print(f"Mascot: {Mascot}")
print(f"Sport: {Sport}")
print(f"Lifetime Losses: {losses}")

school: Drexel
Mascot: Dragons
Sport: Football
Lifetime Losses: 0