使用 Python argparse，如果未指定我的输出文件的名称，我希望使用输入文件的名称

Question

All of the examples use sys.stdout as the default for an optional output file. I would like the default to use the name of my input but with the extension changed. For example, if my input file is example.gif then I would like the default output file to be named example.png . I am trying to write a subclass of argparse.FileType to do this, but would appreciate it if someone has previously solved this problem.

Answer 1

Please directly look at @alkasm comment. It's far better and shorter!!

I use something similar to name my default log files. Could you try this?

def change_file_ext(file_path, new_ext='.out'):
    from pathlib import Path
    in_file_path = Path(file_path)
    out_file_path = Path(Path(in_file_path.parent), Path(in_file_path.stem + new_ext))
    return out_file_path

Note that both in_file_path, out_file_path are instances of pathlib.PosixPath . That should be cross platform

For ex:

print(change_file_ext('/some/dir/filename.in'))
print(change_file_ext('C:\\some\\dir\\filename.in', new_ext='.log'))

Will yeld:

/some/dir/filename.out
C:\some\dir\filename.log