Python: Converting from binary to String

Question

In Python, I have been able to take in a string of 32 bits, and convert this into a binary number with the following code:

def doConvert(string):
    binary = 0
    for letter in string:
        binary <<= 8
        binary += ord(letter)

    return binary

So for the string, 'abcd', this method will return the correct value of 1633837924, however I cannot figure out how to do the opposite; take in a 32 bit binary number and convert this to a string.

If someone could help, I would appreciate the help!

@shuttle87 I'm using Python2

andrewvincent7
– andrewvincent7

2015-11-18 00:15:16 +00:00
Commented Nov 18, 2015 at 0:15 — andrewvincent7
– andrewvincent7, Commented Nov 18, 2015 at 0:15
Is it always a 32bit integer?

shuttle87
– shuttle87

2015-11-18 00:17:31 +00:00
Commented Nov 18, 2015 at 0:17 — shuttle87
– shuttle87, Commented Nov 18, 2015 at 0:17
yeah always a 32bit string being converted.

andrewvincent7
– andrewvincent7

2015-11-18 00:18:17 +00:00
Commented Nov 18, 2015 at 0:18 — andrewvincent7
– andrewvincent7, Commented Nov 18, 2015 at 0:18

shuttle87 · Accepted Answer · 2015-11-18 00:18:37Z

6

If you are always dealing with a 32 bit integer you can use the struct module to do this:

>>> import struct
>>> struct.pack(">I", 1633837924)
'abcd'

Just make sure that you are using the same endianness to both pack and unpack otherwise you will get results that are in the wrong order, for example:

>>> struct.pack("<I", 1633837924)
'dcba'

answered Nov 18, 2015 at 0:18

shuttle87

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4 Comments

andrewvincent7 Over a year ago

Thanks, this works really well! What does the argument, ">I" do? I can't find a reasonable explanation in the docs.

shuttle87 Over a year ago

The I says that it is an unsigned integer. The > says that it is in big-endian format.

Ayush Over a year ago

>>> help(struct) The optional first format char indicates byte order, size and alignment: @: native order, size & alignment (default) =: native order, std. size & alignment <: little-endian, std. size & alignment >: big-endian, std. size & alignment !: same as >

shuttle87 Over a year ago

help(struct) is a good idea! Also the struct documentation has a table with the possible formats.

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