Convert hex to float
In Python 3:
>>> import struct
>>> struct.unpack('!f', bytes.fromhex('41973333'))[0]
18.899999618530273
>>> struct.unpack('!f', bytes.fromhex('41995C29'))[0]
19.170000076293945
>>> struct.unpack('!f', bytes.fromhex('470FC614'))[0]
36806.078125
In Python 2:
>>> import struct
>>> struct.unpack('!f', '41973333'.decode('hex'))[0]
18.899999618530273
>>> struct.unpack('!f', '41995C29'.decode('hex'))[0]
19.170000076293945
>>> struct.unpack('!f', '470FC614'.decode('hex'))[0]
36806.078125
I recommend using the ctypes module which basically lets you work with low level data types. In your case you could say
from ctypes import *
def convert(s):
i = int(s, 16) # convert from hex to a Python int
cp = pointer(c_int(i)) # make this into a c integer
fp = cast(cp, POINTER(c_float)) # cast the int pointer to a float pointer
return fp.contents.value # dereference the pointer, get the float
print convert("41973333") # returns 1.88999996185302734375E1
print convert("41995C29") # returns 1.91700000762939453125E1
print convert("470FC614") # returns 3.6806078125E4
I believe that the ctypes
module makes sense here, because you're essentially asking how to perform low-level bit casting. Your question is basically, how do I tell Python to take some data and interpret that data as if those exact same bits were a different data type?
In C if you had an int and wanted to interpret its bits as a float, you'd do roughly the same thing, taking a pointer and then casting and dereferencing it:
int i = 0x41973333;
float f = *((float*)&i);
and that's exactly what the Python code using the ctypes
library is doing in my example.
I'm guessing this question relates to this one and you are working with 4 bytes rather than 8 hex digits.
"\x41\x91\x33\x33"
is a 4 byte string even though it looks like 16
>>> len("\x41\x91\x33\x33")
4
>>> import struct
>>> struct.unpack(">fff","\x41\x97\x33\x33\x41\x99\x5C\x29\x47\x0F\xC6\x14")
(18.899999618530273, 19.170000076293945, 36806.078125)
If you do need to deal with the string of hexdigits rather than the actual bytes, you can use struct.pack
to convert it, like this
>>> for hx in ["41973333","41995C29","470FC614"]:
... print(struct.unpack(">f",struct.pack(">i",int(hx,16)))[0])
...
18.8999996185
19.1700000763
36806.078125