Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
#!/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
# fix string startwith 0
if integer == 0:
break
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[1] == '-tests':
passed_tests = True
for i in xrange(0, 1000):
passed_tests &= (i == saturate(dehydrate(i)))
print passed_tests
else:
user_input = sys.argv[2]
try:
if sys.argv[1] == '-s':
print saturate(user_input)
elif sys.argv[1] == '-d':
print dehydrate(int(user_input))
else:
print "I don't understand option %s" % sys.argv[1]
except ValueError as e:
print e
@Biglucky

This comment has been minimized.

Copy link

Biglucky commented Jan 27, 2019

Hello,Thank you so much!
This snippet "fix" the "# fix string startwith 0" problem,but it bring the other proble .
The result of dehydrate() function ,always start with '0'

$ python base_62_converter.py -d 5483856748
05z7heO
$ python base_62_converter.py -d 54831258748
0xqkNB6

The input of dehydrate() assumes its an integer.

Thanks!

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.