How do I convert a padded string to an integer while preserving padding?

Question

I followed the great example at Python: Nicest way to pad zeroes to string (4) but now I need to turn that padded string to a padded integer.

I tried:

list_padded=['0001101', '1100101', '0011011', '0011011', '1101111',
             '0000001', '1110111', '1101111', '0111001', '0011011',
             '0011001'] # My padded sting list. 
    
int_list=[int(x) for x in list_padded] # convert the string to an INT

But what I get is a list of integers sans the padding.

Appreciate any direction or suggestions.

Edit:
After learning the revelation that integers don't get padded, I'm thinking a little differently, however it would probably be a good idea to explain more:

I'm working through a basic encryption exercise in a book. It has given me a list of pseudocode to work through;

get cipher string 1-127 and a message, convert both to binary, strip off the 0b, and pad with zeroes.

However it wants me to do the rest WITHOUT XOR! I've gotten that far one line at a time, but now comes this (where the problem begins):

Perform manual XOR operation & append binary 7-bit result to encrypted string
Convert each binary bit of message character and key to an integer
Perform XOR operation on these two bits
Convert literal True and False to binary bit & append to output

I'd love to use the XOR operation but am afraid that doing so would mean I'm not going to learn what I need to.

When you say you want a "padded integer", what do you really need? How are you using such a number? — Karmastan, Jul 12 '10 at 21:08
Karmastan: I'm working through a basic encryption in a book. Rather than using the XOR operation the exercise is leading me through a series of psuedocode intended to teach me how it all works without XOR. So at this point the pseduocode reads: - Get integer ascii value of each character in message (done) - Get binary value of ascii version of character and strip off "0b" (done) And this is where the problem starts: - Check for 7-character length (pad beginning with zeros if necessary) (done) - Convert each binary bit of message character and key to an integer (problem) Thanks! — Jack Tranner, Jul 12 '10 at 21:38
Since your problem has changed so drastically, you should consider opening a new question. — Ignacio Vazquez-Abrams, Jul 12 '10 at 22:37

score 10 · Answer 1 · answered Jul 12 '10 at 21:05

10

Applying idea of padding to integers is meaningless. If you want to print/represent them you need strings, integers just don't have padding.

answered Jul 12 '10 at 21:05

SilentGhost

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ohhhh that's where I'm wrong. Integers don't have padding. I must've missed that tidbit somewhere. Thank you! – Jack Tranner Jul 12 '10 at 21:08

score 5 · Answer 2 · answered Jul 12 '10 at 21:07

Integers don't have a concept of padding, but if you want then you can store both the value and the original length instead of just the value:

int_list = [(int(x), len(x)) for x in list_padded]

Then if you want to reconstruct the original data you have enough information to do so. You may even want to make a custom class to store both these fields instead of using a tuple.

score 0 · Answer 3 · answered Jul 12 '10 at 22:20

Leading zeros is just for data representation:

"{0:b}".format(4).zfill(8)

You can change XOR with other bit-wise operations:

def xor(x, y):
    return (~x & y) | (~y & x)

def bool_xor(x, y):
    return ((not x) and y) or ((not y) and x)

Actually, you can express all bitwise operations with just one logical operation: http://en.wikipedia.org/wiki/Functional_completeness

score -1 · Answer 4 · answered Jul 12 '10 at 21:06

Since the INT type is a number it will be stored without leading zeros. Why would you want to store 675 as 00675? That's meaningless in the realm of integers. I would suggest storing the integers as integers and then only apply the padding when you access them and print them out (or whatever you are doing with them)

How do I convert a padded string to an integer while preserving padding?

4 Answers4