在Python中使用變量值作爲字節數組

Question

我想在Python中實現套接字客戶端。服務器期望前8個字節包含以字節爲單位的總傳輸大小。在C客戶端，我這樣做：

uint64_t total_size = zsize + sizeof (uint64_t); 
uint8_t* xmlrpc_call = malloc (total_size); 
memcpy (xmlrpc_call, &total_size, sizeof (uint64_t)); 
memcpy (xmlrpc_call + sizeof (uint64_t), zbuf, zsize); 

其中zsize和zbuff是我想傳輸的大小和數據。 在Python中，我創建的字節數組是這樣的：

cmd="<xml>do_reboot</xml>" 
result = deflate (bytes(cmd,"iso-8859-1")) 
size = len(result)+8 

什麼是最好的，以填補頭在Python？如果沒有分離值8個字節，它在循環複製

Answer 1

你可以使用struct模塊，將包格式的數據轉換成二進制數據，你想

import struct 
# ...your code for deflating and processing data here... 

result_size = len(result) 
# `@` means use native size, `I` means unsigned int, `s` means char[]. 
# the encoding for `bytes()` should be changed to whatever you need 
to_send = struct.pack("@I{0}s".format(result_size), result_size, bytes(result, "utf-8")) 

參見：

• is there a Python Equivalent to Memcpy
• https://docs.python.org/2/library/struct.html