PYTHON Tutorial

📜 Dictionaries in Python

A dictionary in Python is an unordered collection of data stored in key-value pairs. Unlike lists and tuples, which store a sequence of elements, dictionaries store data as key-value pairs. Each key in a dictionary must be unique, and the values can be of any data type.

🔸 Creating a Dictionary

You can create a dictionary by placing key-value pairs inside curly braces, separated by a colon (:), and each key-value pair is separated by a comma.

# Creating a Dictionary
student = {
  "name": "John",
  "age": 25,
  "city": "New York"
}
print(student)
# Output: {'name': 'John', 'age': 25, 'city': 'New York'}
  

🔸 Accessing Dictionary Values

You can access the values in a dictionary by referencing the key inside square brackets [] or using the get() method.

# Accessing Values
student = {"name": "John", "age": 25, "city": "New York"}
print(student["name"])  # Output: John

# Using get() method
print(student.get("age"))  # Output: 25
  

🔸 Modifying a Dictionary

You can change the value of a key by directly assigning a new value to it, or by using the update() method.

# Modifying Dictionary Values
student = {"name": "John", "age": 25, "city": "New York"}
student["age"] = 26  # Modifies the value of 'age'
print(student)
# Output: {'name': 'John', 'age': 26, 'city': 'New York'}

# Using update() method
student.update({"city": "Los Angeles"})
print(student)
# Output: {'name': 'John', 'age': 26, 'city': 'Los Angeles'}
  

🔸 Adding Items to a Dictionary

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

# Adding Items to a Dictionary
student = {"name": "John", "age": 25, "city": "New York"}
student["gender"] = "Male"  # Adding a new key-value pair
print(student)
# Output: {'name': 'John', 'age': 25, 'city': 'New York', 'gender': 'Male'}
  

🔸 Removing Items from a Dictionary

You can remove items from a dictionary using the del statement or the pop() method. - del: Deletes a specific key-value pair. - pop(): Removes and returns the value associated with a key.

# Removing Items from a Dictionary
student = {"name": "John", "age": 25, "city": "New York", "gender": "Male"}

# Using del statement
del student["age"]
print(student)
# Output: {'name': 'John', 'city': 'New York', 'gender': 'Male'}

# Using pop() method
city = student.pop("city")
print(city)  # Output: New York
print(student)
# Output: {'name': 'John', 'gender': 'Male'}
  

🔸 Dictionary Keys and Values

You can retrieve the keys or values of a dictionary using the keys() and values() methods, respectively.

# Dictionary Keys and Values
student = {"name": "John", "age": 25, "city": "New York"}

# Getting Keys
print(student.keys())
# Output: dict_keys(['name', 'age', 'city'])

# Getting Values
print(student.values())
# Output: dict_values(['John', 25, 'New York'])
  

🔸 Dictionary Length

You can find the number of key-value pairs in a dictionary using the len() function.

# Dictionary Length
student = {"name": "John", "age": 25, "city": "New York"}
print(len(student))  # Output: 3