Python's from_bytes, To_bytes__python

First, let's take a look at two __builtin__ functions

NUM1 = Int.from_bytes (b ', byteorder = ' big ')
num2 = int.from_bytes (b ', byteorder = ' little ')
print (' (%s, '% ' Num1 ', Num1, '), ', ' (%s, '% ' num2 ', num2, ') ')

Result: (NUM1, 12594), (num2, 12849)

BYT1 = (1024). To_bytes (2, Byteorder = ' big ')
byt2 = (1024). To_bytes (Ten, Byteorder = ' big ')
byt3 = ( -1024). to_bytes (byteorder= ' big ')
Lis1 = [' byt1 ', ' byt2 ', ' byt3 ', ' byt4 ']
lis2 = [Byt1, Byt2, Byt3, byt4]
lis3 = Zip (lis1, lis2)
dic = Dict (lis3 )
Print (DIC)

Result

Byt1 ': B ' \x04\x00 '

Byt2 ': B ' \x00\x04\x00\x00\x00\x00\x00\x00\x00\x00 '

Byt3 ': B ' \xff\xff\xff\xff\xff\xff\xff\xff\xfc\x00 '

Byt4 ': B ' \xff\xff\xff\xff\xff\xff\xff\xff\xfc\x00 ' int.from_bytes () function is to convert bytes to int-type number ' 12 ' if not labeled as ASCII value, ' 1 ' = 49 = 0011 0001, ' 2 ' = 50 = 0011 0010, if Byteorder = ' big ', B ' 12 ' = 0010 0001 0010 0010 = 12594; if Byteorder = ' Littlele ', b ' 12 ' = 0011 0010 0011 0001 = 12849. The third parameter is signed representing signed and unsigned, (number). To_bytes () function converts integers to byte

(1024). to_bytes (Byteorder = ' big '), an int, 4 bytes. 1024 = 0000 0000 0000 0000 0000 0100 0000 0000, because the given is 10, so gather 10 bytes, the high level with 6 0000 0000
Occupy, if the last in the 16, 1024 = B ' \x00\x00\x00\ x00\x00\x00\x00\x00x04\x00

Looking at an example:
byt3 = ( -1024). To_bytes (Ten, byteorder= ' big ', signed = ' true '), due to signed = ' true ',-1024 = 1000 ... (one) 0000 0000 0000  0000 0000 0100 0000 0000, Symbol bit 1, ... Omitted
11 0000, because the negative numbers are represented by the complement, so first to 1024 of the inverse code, that is, the symbol bit unchanged, the other bit 0 variable 1,1 to 0, get: 1111 ... (11) 1111 1111 1111 1111 1111 1011 1111 1111, the inverse code + 1, get the complement:
1111 ... (11) 1111 1111 1111 1111 1111 1100 0000 0000, in 16 notation: \xff\xff\xff\xff\xff\xff\xff\xff\xfc\x00

Another example:

NUM3 = int.from_bytes (b ' \xf3\x25 ', byteorder = ' little ')

F3 = 243 (10) = 1111 0011,25 = 37 (10) = 0010 0101,byteorder = ' little ', byte low occupies the main role, get: 0010 0101 1111 0011, get decimal: 9715

NUM3 = int.from_bytes (b ' \xf3\x25 ', Byteorder = ' big ', signed = ' true ')

F3 = 243 (10 in) = 1111 0011,25 = 37 (10) = 0010 0101,byteorder = ' big ', the high position of the byte occupies the main function, obtains: 1111 0011 The 0010 = ' true ', description has
the character number, and the high position is 1, therefore uses the complement: 1000 1100 1101 1011 namely:-3291