python - how to create a program to have an output so it repeats each letter once more as it goes down the word? -

using python how can out out dooggg each letter repeats once more. have tried looks

# program 21 def double(source):   pile = ""   letter in source:     pile = pile+letter+letter     print pile   print pile 

but comes out looking

dd ddoo ddoogg 

 "".join(l*i i,l in enumerate(my_word,1)) 

i think should it