Why This code gives an error " String index out of range " ?

Question

print (" input string")
str1=input()
count=0
for i in range(0,len(str1)):
if(ord(str1[i]+1 == ord(str1[i+1])):
count +=1
else:
count =0
print(count)

Answer 1

Your loop goes until len(str1).

So eventually str1[i] will be the last letter.

But even then you try to access str1[i+1] which is one slot beyond your string.