Dictionaries in Python

In Python, dictionaries are a fundamental data structure used to store and manipulate the data in the form of key-value pairs.

A dictionary is an ordered collection of key-value pairs, where each key is unique and maps to a specific value, we can also call the dictionary an associative array, Hash, and map.

Applications

When a logical relationship between a key: value pair is required, dictionaries can be employed. Keys are distinct identifiers that are used to obtain values.

Creation

You can construct a dictionary in several ways:

Using the 'dict()' constructor:

python
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my_dict = dict()
print(my_dict) # Output: {}

Using the '{}' brackets:

Here, is an example of creating an empty dictionary using the curly brackets:

python
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my_dict = {}
print(my_dict) # Output: {}

Using the key-value pairs:

Here, is an example of creating a dictionary with key-value pairs:

python
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my_dict = {'name': 'John', 'age': 30}
print(my_dict) # Output: {'name': 'John', 'age': 30}

Example

Let’s create an example to demonstrate the dictionary and access the key-value pair of the dictionary.

python
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my_details = {'name': 'letsupdateskills', 'age': 2}
# display the dictionary
print(my_details) # Output: {'name': 'letsupdateskills', 'age': 2}

Dictionary Operations

The following are the common dictionary Operations:

Accessing Value:

In Python, you can access the value of a dictionary through the key using the square [] brackets. Here, is an example to demonstrate this:

python
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my_dict = {'name': 'John', 'age': 30} 
# access name
print(my_dict['name']) # Output: John

Updating a Value:

In Python, you can update a value by assigning a new value to its key. Here, is an example to demonstrate this:

python
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my_dict = {'name': 'John', 'age': 25}
my_dict['age'] = 31
print(my_dict['age']) # Output: 31

Adding a new key-value Pair:

In Python, you can add a new key-value pair by assigning a value to the new key. Here is an example to demonstrate this.

python
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my_dict = {'name': 'Aman', 'age': 25}
my_dict['city'] = 'New York'
print(my_dict) # Output: {'name': 'Aman', 'age': 25, 'city': 'New York'}

Removing a key-value Pair:

In Python, you can remove any key-value pair by using the del statement or pop() method. Here, is an example to demonstrate this.

python
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my_dict = {'name': 'Madhu', 'age': 30}
# use del statement
del my_dict['name']
print(my_dict) # Output: {'name': 'Madhu'}

my_dict = {'name': 'Daisy', 'age': 25}
# use pop() method
my_dict.pop('age')
print(my_dict) # Output: {'name': 'Daisy'}

Checking if a key exists or not:

In Python, you can use the 'in' keyword to check whether a key is exit. Here, is an example to demonstrate this:

python
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my_dict = {'name': 'Daisy', 'age': 30}
# check if the name exists or not in the dictionary
print('name' in my_dict) # Output: True

Dictionary Method

The following is the list of some common dictionary methods:

keys()

It returns a view object that displays a list of all keys in the dictionary. Here, is an example demonstration of this method.

python
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my_dict = {'name': 'Akanksha', 'age': 22} 
print(my_dict.keys()) # Output: dict_values(['Akanksha', 22])

values()

It returns a view object that displays a list of all values in the dictionary. Here, is an example demonstration of this method.

python
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my_dict = {'name': 'Akanksha', 'age': 22}
print(my_dict.values()) # Output: dict_values(['Akanksha', 22])

Items()

It returns a view object that displays a list of all key-value pairs in the dictionary. Here, is an example demonstration of this method.

python
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my_dict = {'name': 'Akanksha', 'age': 22}
print(my_dict.items()) # Output: dict_items([('name', 'Akanksha'), ('age', 22)])

clear()

It removes all key-value pairs of the Python dictionary. Here, is an example demonstration of this method.

python
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my_dict = {'name': 'Daisy', 'age': 26} 
my_dict.clear()
print(my_dict) # Output: {}

copy()

It returns a copy of the dictionary. Here, is an example demonstration of this method.

python
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my_dict = {'name': 'Daisy', 'age': 30}
my_dict_copy = my_dict.copy()
print(my_dict_copy) # Output: {'name': 'Daisy', 'age': 30}