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Dictionary creation

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

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Concepts in Practice

Creating dictionary exercises

1.
What is the correct syntax to create an empty dictionary in Python?
  1. my_dict = ()
  2. my_dict = {}
  3. my_dict = []
2.
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}
3.

How many items does the my_dict object contain?

my_dict = {"a": 1, "b": 2}
  1. 1
  2. 2
  3. 4

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

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Concepts in Practice

dict() function for dictionary creation

4.
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}
5.
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
6.
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"})

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.

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