Python | Convert hexstrings in a list to float

Question

I have data-points of hex-strings in a list.

I tried converting the list to string and then to a byte array. As I try to convert the byte array to float it only returns one value.

Code used is :

byteArrObj = bytearray(n, 'utf-8')
byteObj = bytes(byteArrObj)
byte8=bytearray.fromhex(b)
print(byte8)
floatvalue = struct.unpack('<f', byte8[:4])

This produces a tuple, like `(0.09273222088813782,).

How do I print all the float values from the list?

Just to be clear, are you expecting 0.927322 from 64 EA BD 3D or 0.09273222088813782? — Mark
– Mark, Commented Oct 9, 2020 at 0:14

Karl Knechtel · Accepted Answer · 2020-10-09 00:31:41Z

1

First, let's make a function that converts one of the values:

def hexdump_to_float(text):
    return struct.unpack('<f', bytes.fromhex(text))[0]

Notice:

I skip the step of finding byteArrObj or byteObj from your code, because they had no effect in your code and do not help solve the problem.
I use the type bytes rather than bytearray because we don't need to modify the underlying data. (It's analogous to using a tuple rather than list.)
I do not bother with slicing the data, because we already know there will be only 4 bytes, and because struct.unpack would ignore any extra data in the buffer anyway.
To get the value out of the tuple that struct.unpack returns, I simply index into the tuple. That gives me a single float value.

So this is a simple one-line function, but it helps to make a function anyway since it gives a clear name for what we are doing.

The next step is to apply that to each element of the list. You can do this easily with, for example, a list comprehension:

my_floats = [hexdump_to_float(x) for x in my_hexdumps]

answered Oct 9, 2020 at 0:31

Karl Knechtel

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1 Comment

It worked. Thank you so much. Highly appreciate that.