iban_hash.py

def calculate_polish_hash(b_number):
	polish_template = "PLkk bbbs sssx cccc cccc cccc cccc"
	if b_number[:2] != "PL":
		b_number = "PL" + b_number # prefix
	assert len(b_number.replace(" ", "")) == len(polish_template.replace(" ", ""))
	
	b_number = b_number.replace(" ", "")
	rearranged = b_number[4:] + b_number[:2] + "00"

	converted = "".join([str(int(x, 36)) for x in rearranged])
	remainder = int(converted) % 97

	result = (98 - remainder)
	
	return str(result) if result > 9 else "0" + str(result)