Python float 和 integer 值到字节数组

Question

Problem Solved. Solved code and new problem ( Python bytearray with struct and sending via serial communucation )

I am working on sending data to another program via serial communication.

This receiver program accepts 78 bytes arrays and, each data must be in its own dedicated byte index for the receiver to understand.

Ex: I have an integer altitude value=2500

and the program accepts 4-byte integer values. So I need to fit this integer to these bytes

I wrote a code like this:

import serial

ser = serial.Serial('COM16', 19200, serial.EIGHTBITS, serial.PARITY_NONE, serial.STOPBITS_ONE)

size = 78
array1 = bytearray(size)

altitude=2800.0


check_sum = 0

array1[0] = 0xFF
array1[1] = 0xFF
array1[2] = 0x54
array1[3] = 0x52
array1[4] = 15
array1[5] = 27
array1[6] = 0
array1[7] = 0
array1[8] = 0
array1[9] = 0
array1[10] = 0
array1[11] = 0
array1[12] = 0
array1[13] = 0
array1[14] = 0
array1[15] = 0
array1[16] = 0
array1[17] = 0
array1[17] = 0
array1[19] = 0
array1[19] = 0
array1[20] = 0
array1[21] = 0
array1[22] = 0
array1[23] = 0
array1[24] = 0
array1[25] = 0
array1[26] = 0
array1[27] = 0
array1[28] = 0
array1[29] = 0
array1[30] = 0
array1[31] = 0
array1[32] = 0
array1[33] = 0
array1[34] = 0
array1[35] = 0
array1[36] = 0
array1[37] = 0
array1[38] = 0
array1[39] = 0
array1[40] = 0
array1[41] = 0
array1[42] = 0
array1[43] = 0
array1[44] = 0
array1[45] = 0
array1[46] = 0
array1[47] = 0
array1[48] = 0
array1[49] = 0
array1[50] = 0
array1[51] = 0
array1[52] = 0
array1[53] = 0
array1[54] = 0
array1[55] = 0
array1[56] = 0
array1[57] = 0
array1[58] = 0
array1[59] = 0
array1[60] = 0
array1[61] = 0
array1[62] = 0
array1[63] = 0
array1[64] = 0
array1[65] = 0
array1[66] = 0
array1[67] = 0
array1[68] = 0
array1[69] = 0
array1[70] = 0
array1[71] = 0
array1[72] = 0
array1[73] = 0
array1[74] = 1

array1[76] = 0x0D
array1[77] = 0x0A

for x in range(4, 75):
    check_sum += array1[x]

check_sum % 256

array1[75] = check_sum

ser.write(array1)

The first 4 bytes and last 2 bytes are constant to receive the requirements

My question is

altitude=2800

array1[6] = 0
array1[7] = 0
array1[8] = 0
array1[9] = 0

these 4 bytes are reserved to keep altitude data.

how can I put this altitude data in an array with these byte values?

Answer 1

I would go with the struct module . It is specifically designed to address what you are trying to do.

Answer 2

To expand on Niko's answer, this problem can be solved with Python's builtin struct library . However, you don't seem to have specified anything about the required byte order of your application. For example, the following expressions would produce different results:

big_endian = struct.pack(">f", 0.24)
little_endian = struct.pack("<f", 0.24)

print([*big_endian]) # [62, 117, 194, 143]
print([*little_endian]) # [143, 194, 117, 62], the order is reversed

You should check your receiver requirement of endianness and use the appropriate one in your Python script.