How to add a list to a Python dictionary

Now, let’s see different ways of creating a dictionary of list.

Note that the restriction with keys in Python dictionary is only immutable data types can be used as keys, which means we cannot use a dictionary of list as a key.

# Creating a dictionary

myDict = {[1, 2]: 'Geeks'}

print(myDict)

Output:

1. TypeError: unhashable type: 'list' 

But the same can be done very wisely with values in dictionary. Let’s see all the different ways we can create a dictionary of Lists.

Method #1: Using subscript

# Creating an empty dictionary

myDict = {}

# Adding list as value

myDict["key1"] = [1, 2]

myDict["key2"] = ["Geeks", "For", "Geeks"]

print(myDict)

Output:

1. {'key2': ['Geeks', 'For', 'Geeks'], 'key1': [1, 2]} 

Method #2: Adding nested list as value using append() method.

Create a new list and we can simply append that list to the value.

# Creating an empty dictionary

myDict = {}

# Adding list as value

myDict["key1"] = [1, 2]

# creating a list

lst = ['Geeks', 'For', 'Geeks']

# Adding this list as sublist in myDict

myDict["key1"].append(lst)

print(myDict)

Output:

1. {'key1': [1, 2, ['Geeks', 'For', 'Geeks']]} 

Method #3: Using setdefault()method

Iterate the list and keep appending the elements till given range using setdefault() method.

# Creating an empty dict

myDict = dict()

# Creating a list

valList = ['1', '2', '3']

# Iterating the elements in list

for val in valList:

for ele in range(int(val), int(val) + 2):

myDict.setdefault(ele, []).append(val)

print(myDict)

Output:

1. {1: ['1'], 2: ['1', '2'], 3: ['2', '3'], 4: ['3']} 

Method #4: Using list comprehension

# Creating a dictionary of lists

# using list comprehension

d = dict((val, range(int(val), int(val) + 2))

for val in ['1', '2', '3'])

print(d)

Output:

1. {'1': [1, 2], '3': [3, 4], '2': [2, 3]} 

• Thanks ?.