Jach Feng 在 2023年1月22日 星期日上午11:11:22 [UTC+8] 的信中寫道：
> Fail on command line,
>
> e:\Works\Python>py infix2postfix.py "-4^2+5.3*abs(-2-1)/2"
> usage: infix2postfix.py [-h] [infix]
> infix2postfix.py: error: unrecognized arguments: -4^2+5.3*abs(-2-1)/2
>
> Also fail in REPL,
>
> e:\Works\Python>py
> Python 3.8.8 (tags/v3.8.8:024d805, Feb 19 2021, 13:08:11) [MSC v.1928 32 bit
> (Intel)] on win32
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import argparse
> >>> parser = argparse.ArgumentParser(description='Convert infix notation to
> >>> postfix')
> >>> parser.parse_args("-4^2+5.3*abs(-2-1)/2")
> usage: [-h]
> : error: unrecognized arguments: - 4 ^ 2 + 5 . 3 * a b s ( - 2 - 1 ) / 2
>
> Just can't figure out where is wrong!?
>
> --Jach
Thank you for all your suggestions. From it, I get two solutions for my problem.
1) Modify the sys.argv by inserting an item '--' before parsing it, ie.
sys.argv.insert(1, '--')
args = parser.parse_args()
It works, and maybe more reliable.
e:\Works\Python>py infix2postfix.py "-4^2+5.3*abs(-2-1)/2"
-4 2 ^ 5.3 -2 1 - abs * 2 / +
2) By adding an extra space character before the leading '-' sign, ie.
e:\Works\Python>py infix2postfix.py " -4^2+5.3*abs(-2-1)/2"
-4 2 ^ 5.3 -2 1 - abs * 2 / +
But no idea how it works? and if it can survive in a newer argparse version?:-)
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