Converting a value into 4 byte hex in python

Question

I want to convert any value (that can be negative or positive) into hex. My current method does this.

The read value in this example is 4003.

workingline = stringdb.readline().split(";")
print hex(int(workingline[0]))

This returns

0xfa3

It should be:

0xa30f0000

(Padded with zeros and inverted hexadecimal) IF the value is negative it should be:

0xFEFFFFFF

With the value -2.

I assume padding does not help in this case.

Thank you!

exact duplicate of How to get hex string from signed integer — tylerl
– tylerl, Commented Jun 3, 2012 at 1:24

Ned Batchelder · Accepted Answer · 2012-06-03 01:25:52Z

4

You want the struct module:

>>> struct.pack("<I", 4003).encode('hex')
'a30f0000'

For -2, you'll need to do some other work:

>>> struct.pack("<I", -2 + 2**32).encode('hex')
'feffffff'

A way to do it for any value is:

struct.pack("<I", (value + 2**32) % 2**32).encode('hex')

answered Jun 3, 2012 at 1:18

Ned Batchelder

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3 Comments

This appears to only work for positive values. Do you know another means to make it work for negative values as well?

Alright, thank you! I suppose I will just make a IF statement for two methods. :)

Using "<i" instead of "<I" does the right thing without the + 2**32.