Dictionary

instance of dict class. un-ordered sequences of key:value paired elements. use curly braces {} to create a dict. key should be in single or double quotes. but single is preferred. value could hold any type of data. dictioneries are mutable object.

my_guitar = {
    'brand': 'Ibanez',
    'price': 1000,
    'color': 'black'
}

get element

use dict['key'] to get element from dict. you cannot use dot notation to get element from dict. because dot notation is used to access object attributes. and key in dict is not an attribute.

my_guitar_brand = my_guitar['brand']

print(my_guitar_brand)
# Ibanez

you can also use get('key') to access element from dict and it is recommended. if element is not found in dict, it will return None. you can set a default value to return if element is not found.

my_guitar_price = my_guitar.get('price', 0)

print(my_guitar_price)
# 1000 if element is found
# 0 if element is not found

change element

use dict['key'] = value ato change element in dict.

my_guitar['brand'] = 'Fender'

print(my_guitar)
# {'brand': 'Fender', 'price': 1000, 'color': 'black'}

adding element

use dict['key'] = value to add element in dict.

my_guitar['year'] = 2023

print(my_guitar)
# {'brand': 'Fender', 'price': 1000, 'color': 'black', 'year': 2023}

delete element

use del dict['key'] to delete element from dict.

del my_guitar['year']

print(my_guitar)
# {'brand': 'Fender', 'price': 1000, 'color': 'black'}

methods of dict

there are methods of dict.

• keys() - returns a sequence of keys in dict. which is an instance of dict_keys class. we can convert the sequence to list using list().
• values() - returns a sequence of values in a dict.
• items() - returns a sequence of key:value pairs in dict, which is an instance of dict_items class. we can convert the sequence to list using list().
• clear() - removes all elements from dict.
• copy() - returns a copy of dict.

nested dictionary

value of a key in dict can also be a dict. to access a nested dict, use dict['key']['nested_key'].

access non existence element

return KeyError if key does not exist. But if you use get method no error will be returned, instead returned None.