Dictionary in Python is similar to an associative array in PHP. Dictionary are create using curly braces {} inside it the key is separated with items using a colon (:). For accessing items of a dictionary, the key is been for this. Dictionary is mutable.
Contents
Creating a Dictionary
Dictionary is created using curly braces {} inside it items are stored with a key. Key and item and separated using a colon (:) and items are separated by a comma (,).
Keys should be unique within the dictionary if the same key is reused multiple times in a dictionary then its takes last defined key with the item into the dictionary and remove other. In dictionary tuple can also be used as key in dictionary
Syntax –
dict-variablename = {key1:value1,key2:value2,key3:value3,...}
Example –
dict1 = {'Sonarika':23,'Vishal':24,'Yogesh':22}
dict2 = {('Mayank'):23,'Sunil':22}
print("dict1 : ", dict1)
print("dict2 : ", dict2)
When we execute the above program, it will produce the following output –
dict1 : {'Sonarika':23,'Vishal':24,'Yogesh':22}
dict2 : {('Mayank'):23,'Sunil':22}
Accessing Dictionary
For accessing items from a dictionary, use square brackets [] within it enters a key name.
Syntax –
dict-variablename[key]
Example –
dict1 = {'Sonarika':23,'Vishal':24,'Yogesh':22}
dict2 = {('Mayank'):23,'Sunil':22}
print("dict1['Vishal'] : ", dict1['Vishal'])
print("dict2[('Mayank')] : ", dict2[('Mayank')])
When we execute the above program, it will produce the following output –
dict1['Vishal'] : 24
dict2[('Mayank')] : 23
Update Dictionary
On the basis of the key, we can update existing dictionary.
Syntax –
dict-variablename[key] = value
Example –
dict1 = {'Sonarika':23,'Vishal':24,'Yogesh':22}
dict2 = {('Mayank'):23,'Sunil':22}
dict1['Vishal'] = 25
dict2['Sunil'] = 24
print("dict1 : ", dict1)
print("dict2 : ", dict2)
When we execute the above program, it will produce the following output –
dict1 : {'Sonarika':23,'Vishal':25,'Yogesh':22}
dict2 : {('Mayank'):23,'Sunil':24}
Delete Dictionary
For deleting a dictionary or dictionary item, we use del statement.
Syntax –
del dict-variablename del dict-variablename[key]
Example –
dict1 = {'Sonarika':23,'Vishal':24,'Yogesh':22}
dict2 = {('Mayank'):23,'Sunil':22}
del dict1
del dict2['Sunil']
Dictionary Functions
1. clear – Remove all elements of a dictionary
Syntax – clear()
Example –
dict1 = {'Sonarika':23,'Vishal':24,'Yogesh':22}
print("dict1 : ",dict1.clear(dict1))
Output
dict1 : None
2. copy – Return a copy of a dictionary.
Syntax – copy()
Example –
dict1 = {'Sonarika':23,'Vishal':24,'Yogesh':22}
dict2 = dict1.copy()
print("dict1 : ",dict1)
print("dict2 : ",dict2)
Output
dict1 : {'Sonarika':23,'Vishal':24,'Yogesh':22}
dict2 : {'Sonarika':23,'Vishal':24,'Yogesh':22}
3. fromkeys – Create a new dictionary from sequence and value is optional default value is None. If a value is not set then it assigns None to all keys otherwise set defined value.
Syntax – fromkeys(sequence[,value])
Example –
list1 = ['Sonarika','Vishal','Yogesh']
tuple1 = ('Amit','Sunil','Mayank')
dict1 = dict.fromkeys(list1)
dict2 = dict.fromkeys(tuple1,22)
print("dict1 : ",dict1)
print("dict2 : ",dict2)
Output
dict1 : {'Sonarika': None, 'Vishal': None, 'Yogesh': None}
dict2 : {'Amit': 22, 'Sunil': 22, 'Mayank': 22}
4. get – Return item based on a key in a dictionary. If a key is not available in a dictionary then return default set value, if a default is not defined then return None.
Syntax – get(key[,default]])
Example –
dict1 = {'Sonarika':23,'Vishal':24,'Yogesh':22}
print(dict1.get('Vishal'))
print(dict1.get('Anil','Not found'))
Output
24 Not found
5. items – Return list of a dictionary in which key and values in tuple pair.
Syntax – items()
Example –
dict1 = {'Sonarika': 23, 'Vishal': 24, 'Yogesh': 22}
list1 = list(dict1.items())
print(list1)
Output
[('Yogesh', 22), ('Sonarika', 23), ('Vishal', 24)]
6. keys – Return list of keys in a dictionary.
Syntax – keys()
Example –
dict1 = {'Sonarika': 23, 'Vishal': 24, 'Yogesh': 22}
list1 = list(dict1.keys())
print(list1)
Output
['Yogesh','Sonarika','Vishal']
7. pop – Return and remove an item from a dictionary on the basis of a key.
Syntax – pop(key)
Example –
dict1 = {'Sonarika': 23, 'Vishal': 24, 'Yogesh': 22}
print(dict1.pop('Vishal'))
print(dict1)
Output
24
{'Sonarika': 23, 'Yogesh': 22}
8. popitem – Remove and return a removing item from a dictionary. It remove a random item from a dictionary and not takes any argument.
Syntax – popitem()
Example –
dict1 = {'Sonarika': 23, 'Vishal': 24, 'Yogesh': 22}
print(dict1.popitem)
print(dict1)
Output
{'Yogesh':22}
{'Sonarika': 23, 'Vishal': 24}
9. setdefault – Return value of a given key. if a key is not defined then create a new item in a dictionary and assign the default value.
Syntax – setdefault(key[,default])
Example –
dict1 = {'Sonarika': 23, 'Vishal': 24, 'Yogesh': 22}
print(dict1.setdefault('Yogesh'))
print(dict1.setdefault('Anil',24))
print(dict1)
Output
22
24
{'Yogesh': 22, 'Sonarika': 23, 'Anil': 24, 'Vishal': 24}
10. update – Add a dictionary to another dictionary and doesn’t return any value.
Syntax – update(dictionary)
Example –
dict1 = {'Sonarika': 23, 'Vishal': 24, 'Yogesh': 22}
dict2 = {'Anil': 24, 'Sunil': 23}
dict1.update(dict2)
print(dict1)
print(dict2)
Output
{'Yogesh': 22, 'Sunil': 23, 'Sonarika': 23, 'Anil': 24, 'Vishal': 24}
{'Sunil': 23, 'Anil': 24}
11. values – Return list of values of a dictionary.
Syntax – values()
Example –
dict1 = {'Sonarika': 23, 'Vishal': 24, 'Yogesh': 22}
list1 = list(dict1.values(dict1))
print(list1)
Output
[22,23,24]
