Why does an index error occur when accessing a row?

Question

Python

Good day to all.
I am solving a problem in Python to decode a string.

s_zip = "r12t1x1N15P5i17L2N2u4D8e18V1N1e1N14f1D4H10k2Y19n8R18T13a6B14G18e10L6k20q3l1"
s_out = ""
print(s_zip)
part_of_string = ""
count_str = ""
count = 0
for i in range(0, len(s_zip)):
    j = i+1
    if s_zip[i].isalpha():
        part_of_string = s_zip[i]
    if s_zip[i].isdigit() and s_zip[j].isalpha():
        count_str += s_zip[i]
        count = int(count_str)
        while count < 0:
            s_out += part_of_string
            count -= 1
        count_str = ""
    if s_zip[i].isdigit() and s_zip[j].isdigit():
        count_str += s_zip[i]
print(s_out)

At startup, it swears at s_zip[j].isalpha() with the error IndexError: string index out of range
Help me understand the reason, please.

Answer 1

At the last iteration, you get out of the line, which is what they tell you in plain text.
Let's say the string length is 10. The last iteration is i=9. And j=i+1, that is 10. And your construction s_zip[j] causes an error.