How to check if an item exists in a list in Python
In this tutorial, we will learn how to check if an item exists in a list in Python.
As we know, a list is a collection of different elements.
Certainly, there would be a requirement to know whether an element is present in the list or not.
Sample List :
l = [ ] # empty list l = [23, 45, 67, "hello", "jagannath"] print (l)
Output : [23, 45, 67, 'hello', 'jagannath']
Moreover, in the above code, a list l contains elements namely ( 23, 45, etc )
So, our job is to know whether they are present in the list using different ways.
- with “in” operator
- using a For loop
- dealing with the in-built method list.count( )
Using in operator: check if an item exists in a list in Python
The “in” operator checks whether or not the item exists in the list.
Moreover, it is used with the if statement.
l = [ ] # empty list l = [23, 45, 67, "hello", "jagannath"] if 23 in l: # in operator with if print ("Yes 23 is Present in the list") if "pavan" in l: # there is no element "pavan" in the list print ("pavan is present in the list") else: print ("pavan is not present in the list")
Output : Yes 23 is Present in the list pavan is not present in the list
Using a For loop: check if an item exists in a list in Python
This approach deals with a concept of iterating all elements in the list and checking every element sequentially.
Certainly, this approach is used commonly in all languages.
l = [ ] # empty list l = [23, 45, 67, "hello", "jagannath"] key = "hello" # element to be searched flag = 0 # initial value for i in l: if i == key: # checking every element flag=1 print (key,"is present in list") break if (flag == 0): # only possible if i!=key upto all iterations print (key,"is not present in the list")
Output : hello is present in list
Dealing with the method .count( ) :
The method list.count( item ) is used to get the number of times the item present in the list.
Therefore, this is more of a direct approach.
- If the return value of the above method is 0, then the element is not present.
- Else there is a 100% possibility that element is there in the list.
l = [ ] # empty list l = [23, 45, 67, "hello", "jagannath"] key1 = "hell" # 1st element to be searched key2 = "jagannath" # 2nd element to be searched count_1 = l.count(key1) # count of key1 in the list count_2 = l.count(key2) # count of key2 in the list if (count_1 > 0): print (key1,"is present in the list") # output based on count value else: print (key1,"is not present in the list") if (count_2 > 0): print (key2,"is present in the list") else: print (key2,"is not present in the list")
Output : hell is not present in the list jagannath is present in the list
Concluding, these are the following ways to check the existence of the item in a list.
Certainly, they are helpful while dealing with operations like linear search or binary search or some complex problems.
Leave a Reply