读取二进制数据到可变缓冲区中

为了读取数据到一个可变数组中，使用文件对象的 readinto() 方法。比如：

import os.path

def read_into_buffer(filename):
    buf = bytearray(os.path.getsize(filename))
    with open(filename, 'rb') as f:
        f.readinto(buf)
    return buf
下面是一个演示这个函数使用方法的例子：

>>> # Write a sample file
>>> with open('sample.bin', 'wb') as f:
...     f.write(b'Hello World')
...
>>> buf = read_into_buffer('sample.bin')
>>> buf
bytearray(b'Hello World')
>>> buf[0:5] = b'Hello'
>>> buf
bytearray(b'Hello World')
>>> with open('newsample.bin', 'wb') as f:
...     f.write(buf)
...
11
>>>