Generates strings from chars incrementally

genVarStrings.py

import string, random

# Credit to dunnousername#8672

# return all unique strings from charset y of length l.
# y must be entirely unique chars.
def g(y, l):
  if l == 1:
    # we're just looking for single-char sequences
    # just yield each char in the charset
    yield from y
  elif l > 1:
    # for each char in the charset
    for c in y:
      # for each unique string of length (l-1)
      for d in g(y, l - 1):
        # yield the char concat a smaller unique string (recursive)
        yield c + d
  else:
    pass # should never be called, throw some error here

# actually solve the problem
# x is the number of strings, y is the charset
# l is the starting length
# y must be entirely unique chars
def f(x, y, l=1):
  # if we don't actually need any more strings
  if x <= 0:
    # don't return any, obviously
    return []
  # we need more strings!
  else:
    # number of possible strings of length l in charset y
    z = len(y)**l
    # if there aren't enough to achieve x unique strings
    if x > z:
      # use all unique strings of this length,
      # then recursively call ourselves with larger lengths until we get enough
      return f(z, y, l=l) + f(x - z, y, l=(l+1))
    # elif we have two few strings
    elif x < z:
      # this just calls the next block (else) in a new call of the function
      a = f(z, y, l=l)
      # shuffle it
      random.shuffle(a)
      # choose x random strings from the set of unique strings
      return a[:x]
    # else, the number of unique strings of length l is exactly x
    else:
      # return all of them
      return list(g(y, l))




chars = string.digits
chars = "lI"
print(f(10, chars, 1))
#['l', 'I', 'll', 'lI', 'Il', 'II', 'lII', 'lll', 'IlI', 'IIl']