How to convert integer value to array of four bytes in python

Question

I need to send a message of bytes in Python and I need to convert an unsigned integer number to a byte array. How do you convert an integer value to an array of four bytes in Python? Like in C:

uint32_t number=100; array[0]=(number >>24) & 0xff; array[1]=(number >>16) & 0xff; array[2]=(number >>8) & 0xff; array[3]=number & 0xff; 

Can someone show me how? It is strange to me at first to program without types.

Answer 1

Have a look at the struct module. Probably all you need is struct.pack("I", your_int) to pack the integer in a string, and then place this string in the message. The format string "I" denotes an unsigned 32-bit integer.

If you want to unpack such a string to a tuple of for integers, you can use struct.unpack("4b", s):

>>> struct.unpack("4b", struct.pack("I", 100)) (100, 0, 0, 0) 

(The example is obviously on a little-endian machine.)