Creating a method to read both positive and negative numbers from a file

Question

I want to create a method that can read both positive and negative values from a 4 byte hex. The method that I have now works for only positive values.

def readtoint(read):
    keynumber = read[::-1]
    hexoffset=''
    for letter in keynumber:
        temp=hex(ord(letter))[2:]
        if len(temp)==1:
            temp="0"+temp
        hexoffset += "\\x"+temp
    #value = int(hexoffset, 16)
    return struct.unpack('<i', value)[0]

The above method currently doesn't work because I am trying to make it work with negative numbers. Basically what my program does is it reads 4 bytes from a file, inverts the order, converts it into hex, and then converts the hex into integers. For negative values, I was told to use the struct module but it doesn't seem to work for positive values. Is there a method in python that can handle both negative and positive values?

Thank you!

Your code is a little messed up, the `hex(ord(letter))` isn't doing what you want. — Mark Ransom, Jun 02 '12 at 14:29
What's wrong with this answer to your previous question? http://stackoverflow.com/a/10833610/222914 — Janne Karila, Jun 02 '12 at 14:31

score 1 · Accepted Answer · answered Jun 02 '12 at 14:24

1

Here's a bit of code that will convert 32-bit unsigned to signed:

if value >= 1<<31:
    value -= 1<<32

answered Jun 02 '12 at 14:24

Mark Ransom

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Creating a method to read both positive and negative numbers from a file

1 Answers1