subset sum

def issub(set,n,sum):
if(sum==0):
return True
if(n==0 and sum!=0):
return False
if(set[n-1]>sum):
return issub(set,n-1,sum)
return issub(set,n-1,sum) or issub(set,n-1,sum-set[n-2])
set=[1,2,1,2,1]
sum=5
n=len(set)
if(issub(set,n,sum)==True):
print("Found a subset with sum",sum)
else:
print("No subset found")