CODEWITHSUNDEEP
pythonfloating-pointlong-integer
abhi1610
abhi1610

Reputation: 743

Can not able to convert float from long

I have code which can convert the signed value from unsigned byte-stream. I am able to achieve this. But, when i am trying to convert it to float it can not simply convert but it is rounded up to next int value. Following is my code:

def byte2int(bstr, width=32):
    """
    Convert a byte string into a signed integer value of specified width.
    """
    val = sum(ord(b) << 8*n for (n, b) in enumerate(reversed(bstr)))
    if val >= (1 << (width - 1)):
        val = val - (1 << width)
    return val

str1=('\x00\xff\xa6\x10\xff\xff\xa6\x11\xff\xff\xa6\x12\xff\xff\xa6\x13\xff\xff\xa6\x12\xff\xff\xa6\x11\xff\xff\xa6\x10\xff\xff\xa6\x09\xff\xff\xa6\x08')
res=['','','','','','']
k=4
for l in range(0,6):
    for i in range (0,4):
        res[l]+= str1[i+4*l+k]

Ch1 = (byte2int(res[0]))
print Ch1
print (type(Ch1))
print float(Ch1/100)

Result of this code is following:

-23023
<type 'long'>
 -231.0`

But I want to show this in a -230.23 format. Anyone can guide me.

Upvotes: 1

Views: 163

Answers (2)

Alexander Safronov
Alexander Safronov

Reputation: 76

You must use byte type and module "struct"
Try the following:

import struct    
struct.unpack('f', b'\x00\xff\xa6\x10')

And see help(struct) for more info about converting formats

Upvotes: 0

LaPriWa
LaPriWa

Reputation: 1803

Change the int 100 to long 100.0. This will work. Look at the last line of code:

def byte2int(bstr, width=32):
"""
Convert a byte string into a signed integer value of specified width.
"""
val = sum(ord(b) << 8*n for (n, b) in enumerate(reversed(bstr)))
if val >= (1 << (width - 1)):
    val = val - (1 << width)
return val
str1=('\x00\xff\xa6\x10\xff\xff\xa6\x11\xff\xff\xa6\x12\xff\xff\xa6\x13\xff\xff\xa6\x12\xff\xff\xa6\x11\xff\xff\xa6\x10\xff\xff\xa6\x09\xff\xff\xa6\x08')
res=['','','','','','']
k=4
for l in range(0,6):
    for i in range (0,4):
        res[l]+= str1[i+4*l+k]

Ch1 = (byte2int(res[0]))
print Ch1
print (type(Ch1))
print float(Ch1/100.0)

Upvotes: 2

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