So, what I am trying to do is convert a float to a bytearray but I keep on receiving both no input, and EXTREME slowing/freezing of my computer. My code is
import struct
def float_to_hex(f):
return hex(struct.unpack('<I', struct.pack('<f', f))[0])
value = 5.1 #example value
...
value = bytearray(int(float_to_hex(float(value)), 16)
I found on another article a function to convert floats to hex which is
def float_to_hex(f):
return hex(struct.unpack('<I', struct.pack('<f', f))[0])
and then I converted it from hex to an int. What is the problem with this? How could I better convert it from a float to bin or bytearray?
2 Answers
It depends what you want, and what you are going to do with it. If all you want is a bytearray then:
import struct
value = 5.1
ba = bytearray(struct.pack("f", value))
Where ba is a bytearray. However, if you wish to display the hex values (which I suspect), then:
print([ "0x%02x" % b for b in ba ])
EDIT:
This gives (for value 5.1):
['0x33', '0x33', '0xa3', '0x40']
However, CPython uses the C type double to store even small floats (there are good reasons for that), so:
value = 5.1
ba = bytearray(struct.pack("d", value))
print([ "0x%02x" % b for b in ba ])
Gives:
['0x66', '0x66', '0x66', '0x66', '0x66', '0x66', '0x14', '0x40']
The result I would want from 5.1 is 0x40 a3 33 33 or 64 163 51 51. Not as a string.
To get the desired list of integers from the float:
>>> import struct
>>> list(struct.pack("!f", 5.1))
[64, 163, 51, 51]
Or the same as a bytearray type:
>>> bytearray(struct.pack("!f", 5.1))
bytearray(b'@\xa333')
Note: the bytestring (bytes type) contains exactly the same bytes:
>>> struct.pack("!f", 5.1)
b'@\xa333'
>>> for byte in struct.pack("!f", 5.1):
... print(byte)
...
64
163
51
51
The difference is only in mutability. list, bytearray are mutable sequences while bytes type represents an immutable sequence of bytes. Otherwise, bytes and bytearray types have a very similar API.
