CODEWITHSUNDEEP
pythoncpointerstype-conversion
Brendan K
Brendan K

Reputation: 31

Interpret list of integers as a float in Python

I am attempting to convert a C code snippet into python.

The purpose of said function is to take 4, 8-bit readings from a PLC, and decode them into a single float.

float conv_float_s7_pc(char * plc_real)
{
char tmp[4];
tmp[0] = * (plc_real + 3);
tmp[1] = * (plc_real + 2);
tmp[2] = * (plc_real + 1);
tmp[3] = * (plc_real + 0);
return (* (float *) tmp) ;
}

Is there some Python magic that can perform this function cleanly?

While I am attempting to convert the above function, the more general question is, how would you perform memory "reinterpretations" such as this in python?

Edit

This got me what I needed:

import struct

def conv_to_float(plc):
    temp = struct.pack("BBBB", plc[0], plc[1], plc[2], plc[3])
    output = struct.unpack(">f", temp)[0]
    return output

Upvotes: 2

Views: 800

Answers (1)

John La Rooy
John La Rooy

Reputation: 304205

Use the struct module with the f format character

>>> import struct
>>> plc_real = "1234"
>>> struct.unpack("f", plc_real)[0]
1.6688933612840628e-07

Make sure you use < or > to set the endianness you need

Upvotes: 4

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