I found your topic interesting so I ran the print s[1:4] using Charlie.
This was my code -
pyg = 'ay'
original = raw_input('Enter a word:')
if len(original) > 0 and original.isalpha():
word = original.lower()
first = word
new_word =word + first + pyg
s = new_word
This was the results of the prints I requested.
Enter a word: Charlie
The s[1:4] means # characters from position 1 to position 4. It seems the letter number after the : is excluded from being counted.
Maybe visit stack overflow.com, I found my answer there.
Hope this helped.