How to make a binary string k-bits long

Question

So what the function does is ask for input for the file name, k-bit binary strings, and n number of times to write k-bit binary strings.

def makeStrings():
    fileName = str(input("File Name: "))
    k = input("Bits Input: ")
    n = int(input("Number of Strings: "))
    outputFile = open(fileName, "w")
    counter = 0
    while (counter < n):
        randomNumber = random.randint(0, 9223372036854775808) #that big number is the max representation of a 64bit binary string
        binary = ('{:0' + str(k) + 'b}').format(randomNumber)
        outputFile.write(str(binary) + "\n")
        counter = counter + 1
    outputFile.close()

So what my issue is is that the function works. It does what it is suppose to do except that it doesn't format the binary to be k-bits long. so say for instance I could have any binary representation from random numbers, but I only want them to be k-bits long. so if I make k = 8 it should give me random 8-bit binary strings that are 8 bits long or if I make k = 15 it should give me random 15-bit binary strings.

So say for instance my input is

>>> FileName: binarystext.txt #Name of the file
>>> 16 #number of bits for binary string
>>> 2 #number of times the k-bit binary string is written to the file

It should write to the file the following

1111110110101010
0001000101110100

the same representation would be applied for any bit binary string. 2, 3, 8, 32 etc.

I thought of maybe splitting all the numbers into their represented binary forms so like 0-255 for 8 bit for example and I would just format it if k = 8, but that would mean I would have to do that a ton of times.

Right now what I get is

1010001100000111111001100010000001000000011010111

or some other really long binary string.

niemmi · Accepted Answer · 2016-10-27 03:16:02Z

1

The problem is that width in format string is the minimum width of the field:

width is a decimal integer defining the minimum field width. If not specified, then the field width will be determined by the content.

You could just limit the number you're randomizing to fix the issue:

randomNumber = random.randint(0, 2 ** k - 1)

edited Oct 27, 2016 at 3:16

answered Oct 27, 2016 at 3:08

niemmi

17.3k7 gold badges38 silver badges42 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

wwii · Accepted Answer · 2016-10-27 03:40:50Z

0

Use random.getrandbits() and a format string:

>>> import random
>>> random.getrandbits(8)
41
>>> 
>>> s = '{{:0{}b}}'
>>> k = 24
>>> s = s.format(k)
>>> s.format(random.getrandbits(k))
'101111111001101111100100'
>>>

edited Oct 27, 2016 at 3:40

answered Oct 27, 2016 at 3:09

wwii

23.9k7 gold badges42 silver badges81 bronze badges

1 Comment

niemmi Over a year ago

You need to specify prefix and width in the format string in case that first bit(s) are 0. The second example you provided contains only 20 characters although you randomized 24 bits.

Collectives™ on Stack Overflow

How to make a binary string k-bits long

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related