Dictonaries, Sets & Tuples
Dictionaries
Dictionaries store the data in the form of key-value pairs. Dictionaries are written with curly brackets. Dictionaries are indexed with key values
{'key1':'value1', 'key2':'value2'}
Example
mydict = {'key1':'value1', 'key2':'value2'}
mydict['key1']
In dictionaries, we can have any type of objects.
Dictionary can contain int,float,string,list and dictionaries too..
Lists are ordered collection whereas dictionaries are unordered collection of objects. So, we cannot sort the values of a dictionary.
Dictionaries are mutable.
mydict['key1'] = 'value3'
Popular Methods on Dictionary
Methods | Description |
---|---|
mydict.keys() | to get all keys of dictionary. |
mydict.values() | to get all values of dictionary. |
mydict.items() | to get all items(key:value) of dictionary. |
mydict['key3']='value3' | to add the element to the dictionary. |
mydict.pop('key1') | to remove the element from the dictionary. |
mydict.popitem() | to remove the last inserted elemnet from the dictionary. |
del mydict['key1'] | to remove the element from the dictionary. |
del mydict | to delete the dictionary. |
mydict.clear() | to clear the dictionary, to delete all the elements of the dictionary. |
mydict2 = mydict.copy() | to copy the dictionary. |
mydict2 = dict(mydict) | to copy the dictionary. |
mydict = dict(key1='value1, key2='value2') | to create a dictionary with keyword dict. |
len(mydict) | to get the length of the dictionary |
Tuples
Tuples are similar to lists, the one key difference is tuples are immuatable (Once a element is inside in a tuple, it can't be changed).
Tuples use parenthesis.
mytuple = (1,2,3,4,5)
Popular Methods on Tuples
Methods | Description |
---|---|
mytuple[1] | to get the second element of the tuple , accessing through index number |
len(mytuple) | to find the length of the tuple |
count() | Returns the number of times a specified value occurs in a tuple |
index() | Searches the tuple for a specified value and returns the position of where it was found |
To change the elements of a tuple
x = ("apple", "banana", "cherry")
y = list(x)
y[1] = "kiwi"
x = tuple(y)
print(x)
>> ("apple", "kiwi", "cherry")
Change Tuple Values
Inorder to create a tuple with single element, we need to add a comma after the item, otherwise Python will not recognize it as a tuple.
thistuple = ("apple",)
print(type(thistuple))
>> <class 'tuple'>
#NOT a tuple
thistuple = ("apple")
print(type(thistuple))
>> <class 'str'>
Sets
Set is a unordered and unindexed collection of objects. set is represented using curly braces.
myset = {"apple", "banana", "cherry"}
Set only takes unique elements.
unordered in the sense, we are not sure in which order they appear.
Sets are immutable, that we cannot change the elements of the set, once it is created. We can only add and delete the elements from the set.
Popular Methods on Set
Methods | Description |
---|---|
myset.add('orange') | to add element to the set |
myset.update(['mango', 'grapes']) | to add multiple elements to the set. |
len(myset) | to get the length of the set. |
myset.remove('apple') | to remove an element from the set. |
myset.discard('apple') | to remove an element from the set. |
myset.pop() | to remove the last entered item from the set. |
myset.clear() | to clear all the items of the set. |
del myset | to delete the set. |
myset = set2.union(set1) | union of elements, removes the duplicates. |
myset.update(set1) | to insert the items of set1 into myset. |
myset = set(('apple', 'banana')) | to create a set using set keyword. |