4

For some reason I'm having a heck of a time figuring out how to do this in Python. I am trying to represent a binary string in a string variable, and all I want it to have is

0010111010

However, no matter how I try to format it as a string, Python always chops off the leading zeroes, which is giving me a headache in trying to parse it out.

I'd hoped this question would have helped, but it doesn't really...

Is there a way to force Python to stop auto-converting my string to an integer?

I have tried the following:

val = ""
if (random.random() > 0.50):
  val = val + "1"
else
  val = val + "0"

and

val = ""
if (random.random() > 0.50):
  val = val + "%d" % (1)
else:
  val = val + "%d" % (0)

I had stuck it into an array previously, but ran into issues inserting that array into another array, so I figured it would just be easier to parse it as a string.

Any thoughts on how to get my leading zeroes back? The string is supposed to be a fixed length of 10 bits if that helps.

Edit:

The code:

  def create_string(x):
    for i in xrange(10):        # 10 random populations
      for j in xrange(int(x)):  # population size
        v = ''.join(choice(('0','1')) for _ in range(10))
        arr[i][j] = v

    return arr

  a = create_string(5)
  print a

Hopefully the output I'm seeing will show you why I'm having issues:

[[  10000100 1100000001  101010110     111011   11010111]
 [1001111000 1011011100 1110110111  111011001   10101000]
 [ 110010001 1011010111 1100111000 1011100011 1000100001]
 [  10011010 1000011001 1111111010   11100110  110010101]
 [1101010000 1010110101  110011000 1100001001 1010100011]
 [  10001010 1100000001 1110010000   10110000   11011010]
 [    111011 1000111010    1100101 1101110001  110110000]
 [ 110100100 1100000000 1010101001   11010000 1000011011]
 [1110101110 1100010101 1110001110   10011111  101101100]
 [  11100010 1111001010  100011101    1101010 1110001011]]

The issue here isn't only with printing, I also need to be able to manipulate them on a per-element basis. So if I go to play with the first element, then it returns a 1, not a 0 (on the first element).

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erik
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  • Python will never auto-convert a string into an integer. Also why do you need useless leading zeroes? – Cat Plus Plus Oct 03 '11 at 15:14
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    Um, both of the code examples you've posted should work. What are you doing with the string *after* you create it? How are you outputting it/displaying it? – Amber Oct 03 '11 at 15:15
  • @Amber: They are going into an array (arr), and I'm simply calling 'print arr' – erik Oct 03 '11 at 16:02
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    @Cat, they aren't useless to me, thanks. – erik Oct 03 '11 at 16:02
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    you mean this sort of [array](http://docs.python.org/library/array.html)? Because that says it only stores numerical types, so your string `v` would have to be converted somehow. If you print a number, python starts with the first nonzero digit, unless you can specify the format (eg. "%010d" % n). If you're storing and printing _strings_ as you claim, it shouldn't alter them. – Useless Oct 03 '11 at 16:32
  • @Useless: you hit the nail on the head...the array i was storing it was integer based – erik Oct 03 '11 at 16:38

2 Answers2

7

If I understood you right, you could do it this way:

a = 0b0010111010
'{:010b}'.format(a)

#The output is: '0010111010'

Python 2.7

It uses string format method.

This is the answer if you want to represent the binary string with leading zeros.

If you are just trying to generate a random string with a binary you could do it this way:

from random import choice
''.join(choice(('0','1')) for _ in range(10))

Update

Unswering your update. I made a code which has a different output if compared to yours:

from random import choice
from pprint import pprint

arr = []

def create_string(x):
    for i in xrange(10):       # 10 random populations
        arr.append([])
        for j in xrange(x):  # population size
            v = ''.join(choice(('0','1')) for _ in range(10))
            arr[-1].append(v)
    return arr

a = create_string(5)
pprint(a)

The output is:

[['1011010000', '1001000010', '0110101100', '0101110111', '1101001001'],
 ['0010000011', '1010011101', '1000110001', '0111101011', '1100001111'],
 ['0011110011', '0010101101', '0000000100', '1000010010', '1101001000'],
 ['1110101111', '1011111001', '0101100110', '0100100111', '1010010011'],
 ['0100010100', '0001110110', '1110111110', '0111110000', '0000001010'],
 ['1011001011', '0011101111', '1100110011', '1100011001', '1010100011'],
 ['0110011011', '0001001001', '1111010101', '1110010010', '0100011000'],
 ['1010011000', '0010111110', '0011101100', '1111011010', '1011101110'],
 ['1110110011', '1110111100', '0011000101', '1100000000', '0100010001'],
 ['0100001110', '1011000111', '0101110100', '0011100111', '1110110010']]

Is this what you are looking for?

ovgolovin
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1

How about the following:

In [30]: ''.join('1' if random.random() > 0.50 else '0' for i in xrange(10))
Out[30]: '0000110111'

This gives a ten-character binary string; there's no chopping off of leading zeroes.

If you don't need to vary digit probability (the 0.50 above), a slightly more concise version is:

In [39]: ''.join(random.choice('01') for i in xrange(10))
Out[39]: '0001101001'
NPE
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