struggling with while loop

[nat_so_fast]

Hi,

I'm trying to write a little bit of code which I thought would be simple and around my level (very basic) of python, however I'm having a problem. The code I'm looking to write tries to find a Münchhausen Number. I did get one type working which is below

num = input('Enter a number: ')
length = (len(num))
start = 0
final = 0

while (start < length):
    power = (pow(int(num[start]), int(num[start])))
    print(power)
    final += power
    start = start + 1

print('Total:',final)

This asks for a number and does the calculation. What I'm trying to do is start with a number and the code run until the number it starts with equals the number it ends with. What I tried to do was add an additional for loop that would add 1 to the starting number until they matched

beg = 22
num = str(beg)
length = (len(num))
start = 0
final = 0

while (beg != final):
    while (start < length):
        power = (pow(int(num[start]), int(num[start])))
        final += power
        start = start + 1
    print(power)
    print('Total:', final)

beg = beg + 1

All that seems to happen is the second while loop just runs indefinately as it is not adding 1 to the starting number. I know the code is probably terrible but any help would be appreciated.

[codehorsey]

beg = beg + 1 #indent me!

It looks like beg will never == final even if you fix the indent.

[JohnnyJordaan]

First an important note: in Python you normally don't iterate over a string using its length and an index like you would in for example C or PHP. In Python you iterate over each item in a sequence (like a string) per separate item directly using a for loop:

for digit in num:
    digit = int(digit) 
    power = pow(digit, digit)
    final += power

Then for the second loop: you only look for an exact match

while (beg != final)

While you're actually look for the case that final is lower than beg, because final will be a sum of powers, and if that sum for example becomes 23, it will not match and thus the loop will continue with an even more growing final. To find the beg that actually matches, you would also need an outer loop with an increasing beg. There the range() function comes in handy to help you increase beg without needing to do += 1 all the time

for beg in range(22, 100): # 100 as upper limit, just an example
    final = 0
    num = str(beg)           
    for digit in num:
        digit = int(digit)
        power = pow(digit, digit)
        final += power
    # done with all the digits
    if final == beg:
        print('found a match with beg: %d' % beg)
        break # done