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# Biglucky/base_62_converter.py forked from bhelx/base_62_converter.py Last active Dec 30, 2019

resolve the problem on Python 3.x
 #!/usr/bin/env python # # Converts any integer into a base [BASE] number. I have chosen 62 # as it is meant to represent the integers using all the alphanumeric # characters, [no special characters] = {0..9}, {A..Z}, {a..z} # # I plan on using this to shorten the representation of possibly long ids, # a la url shortenters # # saturate() takes the base 62 key, as a string, and turns it back into an integer # dehydrate() takes an integer and turns it into the base 62 string # import math import sys BASE = 62 UPPERCASE_OFFSET = 55 LOWERCASE_OFFSET = 61 DIGIT_OFFSET = 48 def true_ord(char): """ Turns a digit [char] in character representation from the number system with base [BASE] into an integer. """ if char.isdigit(): return ord(char) - DIGIT_OFFSET elif 'A' <= char <= 'Z': return ord(char) - UPPERCASE_OFFSET elif 'a' <= char <= 'z': return ord(char) - LOWERCASE_OFFSET else: raise ValueError("%s is not a valid character" % char) def true_chr(integer): """ Turns an integer [integer] into digit in base [BASE] as a character representation. """ if integer < 10: return chr(integer + DIGIT_OFFSET) elif 10 <= integer <= 35: return chr(integer + UPPERCASE_OFFSET) elif 36 <= integer < 62: return chr(integer + LOWERCASE_OFFSET) else: raise ValueError("%d is not a valid integer in the range of base %d" % (integer, BASE)) def saturate(key): """ Turn the base [BASE] number [key] into an integer """ int_sum = 0 reversed_key = key[::-1] for idx, char in enumerate(reversed_key): int_sum += true_ord(char) * int(math.pow(BASE, idx)) return int_sum def dehydrate(integer): """ Turn an integer [integer] into a base [BASE] number in string representation """ # we won't step into the while if integer is 0 # so we just solve for that case here if integer == 0: return '0' string = "" while integer > 0: remainder = integer % BASE string = true_chr(remainder) + string integer =int(integer/BASE) return string if __name__ == '__main__': # not really unit tests just a rough check to see if anything is way off if sys.argv == '-tests': passed_tests = True for i in xrange(0, 1000): passed_tests &= (i == saturate(dehydrate(i))) print (passed_tests) else: user_input = sys.argv try: if sys.argv == '-s': print (saturate(user_input)) elif sys.argv == '-d': print (dehydrate(int(user_input))) else: print ("I don't understand option %s" % sys.argv) except ValueError as e: print (e)
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### euclidr commented May 27, 2019 • edited

 hey, I found a problem in this gist, in `dehydrate` function, if `integer` is very big the result will be wrong, because the division result is `float` type which can't represent every integer above `2^53`. In L80 we should use double slash `//` instead of `/`. ``````>>> mu64 = 18446744073709551615 >>> mu64 / 62 % 62 26.0 >>> (mu64 // 62) % 62 34 ``````