10.2: Dictionary Creation

Learning Objectives

By the end of this section you should be able to

• Create a dictionary object with given key/value pairs.

Dictionary creation

Two methods exist for creating an empty dictionary:

• Using curly braces {}. Ex: dict_1 = {}.
• Using the dict() function. Ex: dict_2 = dict().

A dictionary object can also be created with initial key-value pairs enclosed in curly braces. Ex: my_dict = {"pizza": 2, "pasta": 3, "drink": 4} creates a dictionary object my_dict. A key and associated value are separated by a colon, and key-value pairs are separated by commas.

Checkpoint: Creating a dictionary object

Concepts in Practice \(\PageIndex{1}\): Creating dictionary exercises

What is the correct syntax to create an empty dictionary in Python?

1. my_dict = ()
2. my_dict = {}
3. my_dict = []

Answer

b. Curly braces can be used to create an empty dictionary.

Concepts in Practice \(\PageIndex{2}\): Creating dictionary exercises

What is the correct syntax to create a dictionary with one item "one": 1?

1. my_dict = ("one": 1)
2. my_dict = ("one", 1)
3. my_dict = {"one": 1}

Answer

c. {"one": 1} creates a dictionary object with one item "one": 1.

Concepts in Practice \(\PageIndex{3}\): Creating dictionary exercises

How many items does the my_dict object contain?

my_dict = {"a": 1, "b": 2}

1. 1
2. 2
3. 4

Answer

b. Two pairs of items exist in the my_dict dictionary. The two pairs are "a": 1 and "b": 2.

dict() for dictionary creation

A dictionary object can be created with initial key-value pairs using the dict() function.

• Creating a dictionary from a list of tuples. my_list = [("apple", 2), ("banana", 3), ("orange", 4)] my_dict = dict(my_list)
• Creating a dictionary using keyword arguments. my_dict = dict(apple=2, banana=3, orange=4)
• Creating a dictionary from another dictionary. old_dict = {"apple": 2, "banana": 3, "orange": 4} new_dict = dict(old_dict)

Checkpoint: dict() for dictionary initialization

Concepts in Practice \(\PageIndex{4}\): Creating dictionary exercises

What is the correct syntax to create a dictionary with initial values in Python?

1. my_dict = [key1:value1, key2:value2]
2. my_dict = dict(key1=value1, key2=value2)
3. my_dict = {key1=value1, key2=value2}

Answer

b. dict() function, along with keyword arguments, can be used to create a dictionary object.

Concepts in Practice \(\PageIndex{5}\): Creating dictionary exercises

What is the output of the following code?

my_dict = dict({"a": 1})
print(my_dict)

1. {"a": 1}

2. <class, 'dict'>

3. "a"
   1

Answer

a. my_dict is a dictionary with one key-value pair, "a": 1.

Concepts in Practice \(\PageIndex{5}\): Creating dictionary exercises

Which option creates a dictionary with two key-value pairs, "a": "A" and "b": "B"?

1. dict(a: A, b: B)
2. dict([("a", "A"), ("b", "B")])
3. dict({"a" = "A", "b" = "B"})

Answer

b. The dict() function can create a dictionary object from a list of tuples. The first element of each tuple acts as the key, and the second element is the value.

Try It: Personal information dictionary

Create a dictionary, my_info, with three key-value pairs. The keys should be "first name", "last name", and "age" with the values being corresponding information about yourself. Then, print my_info.

Answer

my_info = {"first name": "Parham", "last name": "Aarabi", "age": 46}

print(my_info)