python file.write(字节)工作，但文件缺少字节

Question

我编写了bittorrent客户端，并成功下载了所有文件的所有片段。

在写入文件(mode='wr')之前和之后，我会将文件名、piece_index、写入的字节数和偏移量打印到写入字节的文件中。写完所有文件后，我会关闭这些文件。

但是，当我查看磁盘时，只编写了第一部分。文章完全写入文件0和文件1的开头字节。即使打印语句显示所有剩余的部分都写入文件1，但文件1没有它们。在file.seek，file.write中没有错误。以下是一些输出：

-- first piece --    
offset: 0 piece_index: 0
about to write file 0: offset 0 start 0 nbytes 291
Distributed by Mininova.txt
just wrote 291 bytes at offset 0

about to write file 1: offset 0 start 291 nbytes 1048285    
DF self-extracting archive.exe
just wrote 1048285 bytes at offset 0

-- next piece --
offset: 1048285 piece_index: 1
about to write file 1: offset 1048285 start 1048576 nbytes 1048576
DF self-extracting archive.exe
just wrote 1048576 bytes at offset 1048285

-- next piece --
offset: 2096861 piece_index: 2 file_index: 1
about to write file 1: offset 2096861 start 2097152 nbytes 1048576
DF self-extracting archive.exe
just wrote 1048576 bytes at offset 2096861

守则：

def _write(self, fd, offset, start, num_bytes, row):
    print(fd.name[-30:])
    fd.seek(offset)  
    fd.write(self.buffer[row][start:start+num_bytes].tobytes())
    fd.seek(0)
    print('just wrote {} bytes at offset {}\n'.format(num_bytes, offset))

Answer 1

这应该可以做到：

def _write(self, fd, offset, start, num_bytes, row):
    print(fd.name[-30:])
    fd.seek(offset)
    bytes_ = self.buffer[row][start:start+num_bytes].tobytes()
    fd.write(bytes_)
    fd.flush()
    fd.seek(0)
    print('just wrote {} bytes at offset {}\n'.format(len(bytes_), offset))

1. 计算实际写入的字节：len(bytes_)
2. 写入文件后刷新该文件。您还可以在打开文件时设置buffering=0。