Skip to content
Related Articles

Related Articles

Improve Article
Save Article
Like Article

Python program to Test if all y occur after x in List

  • Last Updated : 16 Nov, 2020

Given a List, test if all occurrences of y are after the occurrence of x in the list.

Input : test_list = [4, 5, 6, 2, 4, 5, 2, 9], x, y = 6, 2 
Output : True 
Explanation : All occurrences of 2 are after 6, hence true.

 Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.  

To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course. And to begin with your Machine Learning Journey, join the Machine Learning - Basic Level Course

Input : test_list = [4, 2, 5, 6, 2, 4, 5, 2, 9], x, y = 6, 2 
Output : False 
Explanation : All occurrences of 2 are not after 6, hence true. 



Method #1 : Using loop + index()

In this, we check for an index of x in the list, and then run a loop to get the occurrence of y, if any y occurs before x index, the result is False.

Python3




# Python3 code to demonstrate working of 
# Test if y occurs after x in List
# Using loop + index()
  
# initializing list
test_list = [4, 5, 6, 2, 4, 5, 2, 9]
  
# printing original lists
print("The original list is : " + str(test_list))
  
# initializing x, y 
x, y = 6, 2
  
# getting index of x 
xidx = test_list.index(x)
  
res = True 
for idx, ele in enumerate(test_list):
      
    # checking for y and comparing index 
    if ele == y and idx < xidx:
        res = False 
        break
  
# printing result 
print("Do all y occur after x : " + str(res))

 
Output:

The original list is : [4, 5, 6, 2, 4, 5, 2, 9]
Do all y occur after x : True

Method #2 : Using all() + index()

In this, we test for all the indices of y using all(), and index() is used to get the index of x in the list.

Python3




# Python3 code to demonstrate working of 
# Test if y occurs after x in List
# Using all() + index()
  
# initializing list
test_list = [4, 5, 6, 2, 4, 5, 2, 9]
  
# printing original lists
print("The original list is : " + str(test_list))
  
# initializing x, y 
x, y = 6, 2
  
# getting index of x 
xidx = test_list.index(x)
  
# checking for all indices of y in list 
res = all(idx > xidx for idx, ele in enumerate(test_list) if ele == y)
  
# printing result 
print("Do all y occur after x : " + str(res))

 
Output:

The original list is : [4, 5, 6, 2, 4, 5, 2, 9]
Do all y occur after x : True



My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!