如何用 Python 覆盖文件中间的一些字节？
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How to overwrite some bytes in the middle of a file with Python?
提问by sebastien
I'd like to be able to overwrite some bytes at a given offset in a file using Python.
我希望能够使用 Python 在文件中的给定偏移量处覆盖一些字节。
My attempts have failed miserably and resulted in:
我的尝试惨遭失败并导致：
- overwriting the bytes at the offset but also truncating the file just after (file mode = "w" or "w+")
- appending the bytes at the end of the file (file mode = "a" or "a+")
- 覆盖偏移量处的字节，但也在紧随其后截断文件（文件模式 = "w" 或 "w+"）
- 在文件末尾附加字节（文件模式 = "a" 或 "a+"）
Is it possible to achieve this with Python in a portable way?
是否有可能以可移植的方式使用 Python 实现这一点？
回答by Ben Blank
Try this:
试试这个：
fh = open("filename.ext", "r+b")
fh.seek(offset)
fh.write(bytes)
fh.close()
回答by tomjen
According to this python pageyou can type file.seek to seek to a particualar offset. You can then write whatever you want.
根据这个 python 页面，您可以输入 file.seek 来寻找特定的偏移量。然后你可以写任何你想要的。
To avoid truncating the file, you can open it with "a+" then seek to the right offset.
为避免截断文件，您可以使用“a+”打开它，然后寻找正确的偏移量。
回答by Johannes Weiss
Very inefficient, but I don't know any other way right now, that doesn't overwritethe bytes in the middle (as Ben Blanks one does):
非常低效，但我现在不知道任何其他方式，这不会覆盖中间的字节（如 Ben Blanks 那样）：
a=file('/tmp/test123','r+')
s=a.read()
a.seek(0)
a.write(s[:3]+'xxx'+s[3:])
a.close()
will write 'xxx' at offset 3: 123456789 --> 123xxx456789
将在偏移量 3 处写入 'xxx'： 123456789 --> 123xxx456789
