Exploring Python Dictionary Methods with Examples: A Comprehensive Guide

Python Dictionary Methods

Python dictionaries are unordered collections of key-value pairs, where each key must be unique. They are implemented as hash tables, providing fast access to values based on their keys. Python provides several built-in dictionary methods to perform common operations on dictionaries. Here are some of the commonly used methods with examples:

1. dict.get(key, default): Returns the value associated with the given key, if it exists in the dictionary, otherwise returns the specified default value.

Example:

python
my_dict = {'name': 'Santi', 'age': 40, 'gender': 'female'}


# Accessing values using get() method

name = my_dict.get('name', 'Unknown')

age = my_dict.get('age', None)

city = my_dict.get('city', 'Unknown')


print(name)  # Output: 'Santi'

print(age)  # Output: 40

print(city)  # Output: 'Unknown'

2. dict.keys(): Returns a view object that displays a list of all the keys in the dictionary.

Example:

python
my_dict = {'name': 'Santi', 'age': 40, 'gender': 'female'}


# Accessing keys using keys() method

keys = my_dict.keys()


print(keys)  # Output: dict_keys(['name', 'age', 'gender'])
print(list(keys))  # Output: ['name', 'age', 'gender']

3. dict.values(): Returns a view object that displays a list of all the values in the dictionary.

Example:

python
my_dict = {'name': 'Santi', 'age': 40, 'gender': 'female'}


# Accessing values using values() method

values = my_dict.values()


print(values)  # Output: dict_values(['Santi', 40, 'female'])
print(list(values))  # Output: ['Santi', 40, 'female']

4. dict.items(): Returns a view object that displays a list of all the key-value pairs in the dictionary as tuple pairs.

Example:

python
my_dict = {'name': 'Santi', 'age': 40, 'gender': 'female'}


# Accessing key-value pairs using items() method

items = my_dict.items()


print(items)  # Output: dict_items([('name', 'Santi'), ('age', 40), ('gender', 'female')])

print(list(items))  # Output: [('name', 'Santi'), ('age', 40), ('gender', 'female')]

5. dict.update(other_dict): Updates the dictionary with key-value pairs from another dictionary.

Example:

python
my_dict = {'name': 'Santi', 'age': 40}


# Updating dictionary using update() method

my_dict.update({'age': 41, 'city': 'Kolkata'})


print(my_dict)  # Output: {'name': 'Santi', 'age': 41, 'city': 'Kolkata'}

6. dict.pop(key, default): Removes and returns the value associated with the given key from the dictionary. If the key does not exist, it returns the specified default value.

Example:

python
my_dict = {'name': 'Santi', 'age': 40, 'gender': 'female'}


# Removing a key-value pair using pop() method

age = my_dict.pop('age', None)

city = my_dict.pop('city', 'Unknown')


print(age)  # Output: 40

print(city)  # Output: 'Unknown'

print(my_dict)  # Output: {'name': 'Santi', 'gender': 'female'}

7. dict.clear(): Removes all the key-value pairs from the dictionary and display empty dictionary.

Example:

python
my_dict = {'name': 'Santi', 'age': 40, 'gender': 'female'}


# Clearing dictionary using clear() method

my_dict.clear()


print(my_dict)  # Output: {}

8. dict.copy(): Creates a shallow copy of the dictionary, i.e., a new dictionary with the same key-value pairs but a different memory address.

Example:

python
my_dict = {'name': 'Santi', 'age': 40, 'gender': 'female'}


# Creating a shallow copy of the dictionary using copy() method
my_dict_copy = my_dict.copy()


print(my_dict_copy)  
# Output: {'name': 'Santi', 'age': 40, 'gender': 'female'}

9. dict.setdefault(key, default): Returns the value associated with the given key, if it exists in the dictionary. Otherwise, sets the key with the specified default value and returns the default value.

Example:

python
my_dict = {'name': 'Santi', 'age': 40}


# Setting a default value for a key using setdefault() method

gender = my_dict.setdefault('gender', 'Unknown')

city = my_dict.setdefault('city', 'Kolkata')


print(gender)  # Output: 'Unknown'

print(city)  # Output: 'Kolkata'

print(my_dict)  
# Output: {'name': 'Santi', 'age': 40, 'gender': 'Unknown', 'city': 'Kolkata'}

10. dict.fromkeys(iterable, value): Creates a new dictionary with keys from the specified iterable and values set to the given value.

Example:

python
keys = ['name', 'age', 'gender']

my_dict = dict.fromkeys(keys, 'Unknown')


print(my_dict)  
# Output: {'name': 'Unknown', 'age': 'Unknown', 'gender': 'Unknown'}

These are some of the commonly used dictionary methods in Python. There are many other methods available in the Python documentation.