Question

我想这可以通过代码和评论来解释：

import struct

class binary_buffer(str):
    def __init__(self, msg=""):
        self = msg
    def write_ubyte(self, ubyte):
        self += struct.pack("=B", ubyte)
        return len(self)

Output
>> bb = binary_buffer()
>> bb # Buffer starts out empty, as it should
''
>> bb.write_ubyte(200)
1   # We can see that we've successfully written one byte to the buffer
>> bb
''  # Huh? We just wrote something, but where has it gone?

Answer 1

str是不可变的。因此，

self += struct.pack("=B", ubyte)

评估为

self = self + struct.pack("=B", ubyte)

这为名称self指定了一个新值，但self只是一个与其他名称一样的名称。一旦方法退出，名称（和相关对象）就会被遗忘。

您需要bytearray：

>>> bb = bytearray()
>>> bb.append(200)
>>> bb
bytearray(b'\xc8')

通过扩展Python str来创建缓冲类

1 个答案: