Python
About Lesson

A dictionary in Python is a collection of key-value pairs. Each key is unique and maps to a value. Dictionaries are mutable, meaning they can be changed after they are created. They are defined using curly braces {} and key-value pairs are separated by a colon :.

Python dictionary is an unordered collection of items. In a dictionary, each item has a key/value pair.

 

Creating a Dictionary

You can create a dictionary by placing a comma-separated sequence of key-value pairs within curly braces.

Example:

users = {'name':'Junaid', 'age':25, 'city' : 'Nashik'}
print(users)
print(type(users))

user_info = {
    'name' : 'Junaid Shaikh',
    'age' : 24,
    'skills' : ['a', 'v'],
    'tunes' : ['t', 'tv'], 
}
print(user_info['skills'])

 

Accessing Values

You can access the value associated with a key using square brackets [].

# access data from dictionaries 
print(users['name'])

 

Modifying Values

You can modify the value associated with a key by assigning a new value to that key.

# Modifying values in a dictionary 
users["age"] = 26
print(users["age"]) # Output: 26

 

Adding New Key-Value Pairs

You can add a new key-value pair to a dictionary by simply assigning a value to a new key.

# Adding new key-value pairs
users["email"] = "infovistarindia@gmail.com"
print(users)

 

Removing Key-Value Pairs

You can remove a key-value pair using the del statement or the pop() method.

# Removing key-value pairs
del users["city"]
print(users)

# Using pop() method
age = users.pop("age")
print(age) # Output: 26
print(users)

 

Iterating Over a Dictionary

You can iterate over the keys, values, or key-value pairs in a dictionary.

# Iterating over keys
for key in users:
print(key, users[key])

# Iterating over values
for value in users.values():
print(value)

# Iterating over key-value pairs
for key, value in users.items():
print(key, value)

 

Dictionary Methods

Python dictionaries come with several built-in methods. Here are a few useful ones:

Function Description
dict.clear() removes all elements of dictionary dict
dict.copy() returns a shallow copy of dictionary dict
dict.items() returns a list of dict’s (key, value) tuple pairs
dict.setdeafult(key, default=Nonre) similiar to get(), but will set dict[key] = default
dict.update(dict2) adds dictionary dict2’s key-values pairs to dict
dict.keys() returns list of dictionary dict’s keys
dict.values() returns list of dictionary dict’s values

 

# Using dictionary methods
print(users.get("name")) # Output: Junaid
print(users.get("address", "Address not found")) # Output: Address not found
print(list(users.keys())) # Output: ['name', 'email']
print(list(users.values())) # Output: ['Junaid', 'infovistarindia@gmail.com']
print(list(users.items())) # Output: [('name', 'Junaid'), ('email', 'infovistarindia@gmail.com')]