Dictionary in Python

 

Dictionary in Python

A dictionary in Python is a built-in, mutable, collection data structure that stores data in key-value pairs.

A dictionary is a collection which is ordered*, changeable and do not allow duplicates. Dictionaries are written with curly brackets, and have keys and values:

Ex.1

dict ={

  "Name": "AD Computer Campus",

  "Blog": "Python",

  "year": 2019,

}

print(dict)

Output

{'Name': 'AD Computer Campus', 'Blog': 'Python', 'year': 2019}

Ex.2

dict ={

  "Name": "AD Computer Campus",

  "Blog": "Python",

  "year": 2019,

}

print(dict[Name])

Output

AD Computer Campus

Duplicates Not Allowed

dict ={

  "Name": "AD Computer Campus",

  "Blog": "Python",

  "year": 2019,

  "year": 2022,

}

print(dict)

Output

{'Name': 'AD Computer Campus', 'Blog': 'Python', 'year': 2022}

Dictionary Length

dict ={

  "Name": "AD Computer Campus",

  "Blog": "Python",

  "year": 2019,

}

print(len(dict))

Output

3

Dictionary String, int, Boolean, and list data types:

Prog 1.

dict ={

  "Name": "AD Computer Campus",

  "Blog": "Python",

  "year": 2019,

  "colors": ["red", "white", "blue"]

}

print(dict)

Output

{'Name': 'AD Computer Campus', 'Blog': 'Python', 'year': 2019, 'colors': ['red', 'white', 'blue']}

Prog 2.

info=    {

"Name" : "Rahul",

"Subject" : ["python","C","Java"],

"Topic" : ("dict","set"),

"age" : 35,

"is _adult" : True,

"marks" : 94.6

}

print(info)

Output

{'Name': 'Rahul', 'Subject': ['python', 'C', 'Java'], 'Topic': ('dict', 'set'), 'age': 35, 'is _adult': True, 'marks': 94.6}

Nested dictionary

A nested dictionary in Python is a dictionary where the values are themselves other dictionaries, allowing for the storage of complex, hierarchical data. They are useful for organizing related information, such as records of multiple students or employee.

Ex. 1

students = {

    'student1': {

        'name': 'Rahul',

        'age': 30,

        'grade': 'A'

    },

    'student2': {

        'name': 'Neha',

        'age': 25,

        'grade': 'B'

    }

}

print(students["student1"])

Output

{ 'name' : 'Rahul' , 'age': 30, 'grade': 'A' }

Ex. 2

students = {

    'student1': {

        'name': 'Rahul',

        'age': 30,

        'grade': 'A'

    },

    'student2': {

        'name': 'Neha',

        'age': 25,

        'grade': 'B'

    }

}

print(students)

Output

{ 'name' : 'Rahul' , 'age': 30, 'grade': 'A' },{ 'name': 'Neha', 'age': 25, 'grade': 'B' }

Keys() method 

The keys() method will return a list of all the keys in the dictionary.

Ex. 

students = {

    'student1': {

        'name': 'Alice',

        'age': 30,

        'grade': 'A'

    },

    'student2': {

        'name': 'Bob',

        'age': 25,

        'grade': 'B'

    }

}

print(students.keys())

Output

dict_keys(['student1','student2'])

Values() Method 

The values() method will return a list of all the values in the dictionary.

Ex. 

students = {

    'student1': {

        'name': 'Alice',

        'age': 30,

       'grade': 'A'

    },

    'student2': {

       'name': 'Bob',

        'age': 25,

        'grade': 'B'

    }

}

print(students.values())

Output

dict_values([{'name': 'Rahul', 'age': 30, 'grade': 'A'}, {'name': 'Neha', 'age': 25, 'grade': 'B'}])

 Items() Method 

The items() method will return each item in a dictionary, as tuples in a list.

Ex. 

students = {

    'student1': {

        'name': 'Kunal',

        'age': 30,

        'grade': 'A'

    },

    'student2': {

        'name': 'Raj',

        'age': 25,

        'grade': 'B'

    }

}

print(students.items())

Output

dict_items([('student1', {'name': 'Kunal', 'age': 30, 'grade': 'A'}), ('student2', {'name': 'Raj', 'age': 25, 'grade': 'B'})])

 Get() Method 

Return the key according to value.

Ex. 

car = {

  "brand": "Tata",

  "model": "Punch",

  "year": 2024

}

x = car.get("brand")

print(x)

Output

Tata

Update() Method 

The update() method will update the dictionary with the items from a given argument. If the item does not exist, the item will be added.

Ex. 

car = {

  "brand": "Ford",

  "model": "Mustang",

  "year": 1964

}

car.update({"color": "red"})

print(car)

Output

{'brand': 'Ford', 'model': 'Mustang', 'year': 1964, 'color': 'red'}

Remove Dictionary Items

There are several methods to remove items from a dictionary:

• The pop() method removes the item with the specified key name.

• The popitem() method removes the last inserted item.

• The del keyword removes the item with the specified key name.

• The del keyword can also delete the dictionary completely.

Ex. 

car = {

  "brand": "Tata",

  "model": "Punch",

  "year": 2024

}

car.pop("model")

print(car)

Output

{'brand': 'Tata', 'year': 2024}

Let's Practices-

1) Store Following word meaning in a Python Dictionary:

table: "a piece furniture" , "list of facts & figures"

cat : "a small animal"

Solution-

dict= {

"cat" : "a small animal"

"table": ["a piece furniture", "list of facts & figures"]

}

Output

{'cat' : 'a small animal' , 'table': ['a piece furniture', 'list of facts & figures']}