s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_.-"

list = []
def i(c, l):
  for x in s[:]:
    if len(c) == l-1:
      list.append(c+x)
    else:
      i(c+x, l)

i("hi", 4)
print list