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Dictionary is the built in data type in python.
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we saw list is indexed range from 0 to n-1
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Unlike List, Dictionaries are indexed with keys. Dictionary is a set of key:value pair. With the help of key we can access value
Define Dictionary
syntax to define dictionary is,
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
In above definition, "dict_example" is the variable name of the dictionary. fruit, vegetable, animal are the keys of the dictionary(dict_example) and cherry, tomato, tiger are the respective values of the keys.
Printing Dictionary
By using print() method, we can print variables in python, so to print dictionary we use print() method
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
print(dict_example)
output: {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
Accessing value with key
We can print the value of particular key,
dict[key] will give the value of that key
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
print(dict_example['vegetable'])
output: tomato
'tomato' is the value of 'vegetable' key in dict_example.
We can use get() method to access item
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
print(dict_example.get('animal'))
output: tiger
Change the value
We can change the value of particular key, by simply assigning value to the key
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
dict_example['animal'] = 'lion'
print(dict_example)
{'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'lion'}
Inserting new key:value
As we understand, each item in the dictionary is a key:value pair, If we want to insert new item into the dictionary we want to insert key and value like below
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
dict_example['flower'] = 'rose'
print(dict_example)
Output : {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger', 'flower': 'rose'}
'flower' is the key, 'rose' is the value for that key
Deleting item in dictionary
we can delete whole dictionary or single item by using 'del' keyword
Deleting whole dictionary
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
del dict_example
print(dict_example)
Output : NameError: name 'dict_example' is not defined
In the above output we got NameError while printing 'dict_example' because we deleted 'dict_example' in previous line
Deleting specified item in dictionary with 'del' keyword
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
del dict_example['animal']
print(dict_example)
Output : {'fruit': 'cherry', 'vegetable': 'tomato'}
In the above example we deleted the item 'animal'
Deleting specified item in dictionary with pop() method
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
dict_example.pop('animal')
print(dict_example)
Output : {'fruit': 'cherry', 'vegetable': 'tomato'}
popitem() will remove last inserted item in the dictionary
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
dict_example.popitem()
print(dict_example)
Output : {'fruit': 'cherry', 'vegetable': 'tomato'}
clear() method will remove the all items in the dictionary
Python code
dict_example = {'fruit': 'cherry', 'vegetable': 'tomato', 'animal': 'tiger'}
dict_example.clear()
print(dict_example)
Output : {}