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Python | Check if one list is subset of other
  • Last Updated : 11 Mar, 2019

Sometimes we encounter the problem of checking if one list is just an extension of the list i.e just a superset of one list. This kind of problems are quite popular in competitive programming. Having shorthands for it helps the cause. Lets discuss various ways to achieve this particular task.

Method #1 : Using all()
all() is used to check all the elements of a container in just one line. Checks for all the elements of one list for existence in other list.




# Python3 code to demonstrate 
# to check if list is subset of other
# using all()
  
# initializing list
test_list = [9, 4, 5, 8, 10]
sub_list = [10, 5, 4]
  
# printing original lists
print ("Original list : " + str(test_list))
print ("Original sub list : " + str(sub_list))
  
# using all() to 
# check subset of list 
flag = 0
if(all(x in test_list for x in sub_list)):
    flag = 1
      
# printing result
if (flag) :
    print ("Yes, list is subset of other.")
else :
    print ("No, list is not subset of other.")

Output :

Original list : [9, 4, 5, 8, 10]
Original sub list : [10, 5, 4]
Yes, list is subset of other.

Method #2 : Using set.issubset()
The most used and recommended method to check for a sublist. This function is tailor made to perform the particular task of checking if one list is a subset of another.




# Python3 code to demonstrate 
# to check if list is subset of other
# using issubset()
  
# initializing list
test_list = [9, 4, 5, 8, 10]
sub_list = [10, 5]
  
# printing original lists
print ("Original list : " + str(test_list))
print ("Original sub list : " + str(sub_list))
  
# using issubset() to 
# check subset of list 
flag = 0
if(set(sub_list).issubset(set(test_list))):
    flag = 1
      
# printing result
if (flag) :
    print ("Yes, list is subset of other.")
else :
    print ("No, list is not subset of other.")

Output :



Original list : [9, 4, 5, 8, 10]
Original sub list : [10, 5]
Yes, list is subset of other.

Method #3 : Using set.intersection()
Yet another method dealing with sets, this method checks if the intersection of both the lists ends up to be the sub list we are checking. This confirms that one list is a subset of the other.




# Python3 code to demonstrate 
# to check if list is subset of other
# using intersection()
  
# initializing list
test_list = [9, 4, 5, 8, 10]
sub_list = [10, 5]
  
# printing original lists
print ("Original list : " + str(test_list))
print ("Original sub list : " + str(sub_list))
  
# using intersection() to 
# check subset of list 
flag = 0
if((set(sub_list) & set(test_list))== set(sub_list)):
    flag = 1
      
# printing result
if (flag) :
    print ("Yes, list is subset of other.")
else :
    print ("No, list is not subset of other.")

Output :

Original list : [9, 4, 5, 8, 10]
Original sub list : [10, 5]
Yes, list is subset of other.


Method #4 : Using iteration and counter

Using count of element in both lists to check whether the second list is a subset of the first list.




# Python3 code to demonstrate 
# to check if list is subset of other
  
#Importing
from collections import Counter
  
def checkInFirst(a, b):
     #getting count
    count_a = Counter(a)
    count_b = Counter(b)
  
    #checking if element exsists in second list
    for key in count_b:
        if key not in  count_a:
            return False
        if count_b[key] > count_b[key]:
            return False
    return True
  
# initializing list
a = [1, 2,4,5]
b = [1, 2,3]
  
#Calling function
res = checkInFirst(a, b)
  
#Printing list
print ("Original list : " + str(a))
print ("Original sub list : " + str(b))
  
if res==True :
    print ("Yes, list is subset of other.")
else :
    print ("No, list is not subset of other.")
      
#Added by Paras Jain(everythingispossible)

Output :

Original list : [1, 2, 4, 5]
Original sub list : [1, 2, 3]
No, list is not subset of other.


Method #5 : Using set index




# Python3 code to demonstrate 
# to check if list is subset of other
  
# initializing list
one = [1,2,3,4,5]
two = [1,2]
  
#using set to find if element exsists in another list
result = set(x in one for x in two)
  
flag = 0
  
for ans in result:
    if ans == False:
        flag=1
  
#Printing list
print ("Original list : " + str(one))
print ("Original sub list : " + str(two))
  
if flag==0:
    print("Yes, list is subset of other.")
else:
    print("No, list is not subset of other.")
  
#Added by Paras Jain(everythingispossible)

Output :

Original list : [1, 2, 3, 4, 5]
Original sub list : [1, 2]
Yes, list is subset of other.

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