Python - 如何正确获取文件中两个偏移量之间的内容？

Question

I'm trying to get content between two offset (essentially part of a file). For that, I found fileslice to be useful.

For testing I'm using a file called hello with the string:

helloworld

I left a newline deliberately since I'm doing testing on different things.

Using this code:

from fileslice import Slicer
import sys

r = open('hello', 'r')

slicer = Slicer(r)

start = int(sys.argv[1])
size = int(sys.argv[2])
fileslice = slicer (start, size)
    
sys.stdout.write(fileslice.read())

Anyway, the problem I'm facing is that, when using certain offset range, it seems like the wrong character represented by the offset get displayed...:

:~/fileslice$ wc -c hello # using wc to check the size
11 hello
:~/fileslice$ python -u "/home/user/fileslice/testslice.py" 0 11 | xxd # works
00000000: 6865 6c6c 6f77 6f72 6c64 0a              helloworld.
:~/fileslice$ python -u "/home/user/fileslice/testslice.py" 0 10 | xxd # works
00000000: 6865 6c6c 6f77 6f72 6c64                 helloworld
:~/fileslice$ python -u "/home/user/fileslice/testslice.py" 1 10 | xxd # doesn't work as expected
00000000: 656c 6c6f 776f 726c 640a                 elloworld.

Here I'm using the previously mentioned test file and code and pipe the output to wc (to check the size) then after that, do a couple testing and checking the output in Hex with xxd .

As it can be seen, the one commented "works" work as expected, as in, i can get the content between the two offset just fine.

But for the last one, where i wanted to get content between the char e (in this case offset 1 ) which "work" but then, notice that the previously discarded newline (offset 10 ) appear again, contrary to the previous test which worked fine/as excepted...

How can i correctly get content of a file using two offset? (start/end)

Answer 1

大小是两个偏移量之间的距离，即结束减去开始。

size = int(sys.argv[2]) - int(sys.argv[1])