Dictionaries
Unordered collection of items.
Every dictionary item is a Key-value pair.

Creating a Dictionary
Created by enclosing items within {curly} brackets
Each item in dictionary has a key – value pair separated by a comma.
Code
dict_a = {
"name": "Teja",
"age": 15
}
Key – Value Pairs
Code
dict_a = {
"name": "Teja",
"age": 15
}
In the above dictionary, the
- keys are name and age
- values are Teja and 15
Collection of Key-Value Pairs
Code
dict_a = { "name": "Teja",
"age": 15 }
print(type(dict_a))
print(dict_a)
Output
<class ‘dict’>
{‘name’: ‘Teja’,’age’: 15}
Immutable Keys
Keys must be of immutable type and must be unique.
Values can be of any data type and can repeat.
Code
dict_a = {
"name": "Teja",
"age": 15,
"roll_no": 15
}
Creating Empty Dictionary
Code – 1
dict_a = dict()
print(type(dict_a))
print(dict_a)
Output
<class ‘dict’>
{}
Code – 2
dict_a = {}
print(type(dict_a))
print(dict_a)
Output
<class ‘dict’>
{}
Accessing Items
To access the items in dictionary, we use square bracket [ ] along with the key to obtain its value.
Code
dict_a = {
'name': 'Teja',
'age': 15
}
print(dict_a['name'])
Output
Teja
Accessing Items – Get
The
get() method returns
None if the key is not found.
Code
dict_a = {
'name': 'Teja',
'age': 15
}
print(dict_a.get('name'))
Output
Teja
KeyError
When we use the square brackets
[] to access the key-value, KeyError is raised in case a key is not found in the dictionary.
Code
dict_a = {'name': 'Teja','age': 15 }
print(dict_a['city'])
Output
KeyError: ‘city’
If we use the square brackets [], KeyError is raised in case a key is not found in the dictionary. On the other hand, the get() method returns None if the key is not found.
Code
dict_a = {
'name': 'Teja',
'age': 15
}
print(dict_a.get('city'))
Output
None
Membership Check
Checks if the given key exists.
Code
dict_a = {
'name': 'Teja',
'age': 15
}
result = 'name' in dict_a
print(result)
Output
True
Operations on Dictionaries
We can update a dictionary by
- Adding a key-value pair
- Modifying existing items
- Deleting existing items
Adding a Key-Value Pair
Code
dict_a = {'name': 'Teja','age': 15 }
dict_a['city'] = 'Goa'
print(dict_a)
Output
{‘name’: ‘Teja’, ‘age’: 15, ‘city’: ‘Goa’}
Modifying an Existing Item
As dictionaries are mutable, we can modify the values of the keys.
Code
dict_a = {
'name': 'Teja',
'age': 15
}
dict_a['age'] = 24
print(dict_a)
Output
{‘name’: ‘Teja’, ‘age’: 24}
Deleting an Existing Item
We can also use the
del keyword to remove individual items or the entire dictionary itself.
Code
dict_a = {
'name': 'Teja',
'age': 15
}
del dict_a['age']
print(dict_a)
Output
{‘name’: ‘Teja’}