I think you want to do something like:
from string import ascii_uppercase
buttons = [form.Button("btn", id="btn{0}".format(char), value=char,
html=movie, class_="btn{0}".format(char))
for char, movie in zip(ascii_uppercase, movies)]
my_form = form.Form(buttons)
This uses the letters in string.ascii_uppercase
to label each item in movies
.