How to make argparse accept "-4^2+5.3*abs(-2-1)/2" string argument?

[Jach Feng]

Thomas Passin 在 2023年1月22日 星期日下午1:30:39 [UTC+8] 的信中寫道：
> On 1/21/2023 10:11 PM, Jach Feng wrote: 
> > 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!?
> It just doesn't work like that. If you download the package, there is 
> only one python file, __init__.py. This file contains one class. It 
> has a demo at the end, commented out. If you uncomment those lines and 
> run the file, you get a result printed. 
> 
> These remarks are based on downloading the link for the source 
> distribution from Pypi 
> (https://pypi.org/project/infix2postfix/). When I installed it with 
> pip, nothing seems to have gotten installed although pip went through 
> the motions and claimed it was. So I just downloaded the source package. 
> 
> The test expression is "-(a*b)+(c+d)-(a+b+c+d)". The test output for 
> this is "ab*-cd++ab+c+d+-". 
> 
> If you substitute your expression, the result is 
> 
> abs1-2-*2/3.5+2^4- 
> 
> This may or may not be correct. I'm not sure but I think it's as 
> intended except for reversing "3.5". But maybe that's right, I'm not 
> too sure. Notice that this file is in its first release, version 0.0.1 
> - the metadata that says it's 'Development Status :: 5 - 
> Production/Stable' seems to be bogus. So it may very well be buggy. 
> 
> At any rate, if you want to use it in a program that can accept 
> arguments, you will have to write that part yourself. And the 
> expression you feed it would need to be a single string, meaning it has 
> to be quoted on the command line as you have done (although on Windows 
> you should be using double quotes instead of single quotes). 
> 
> As for argparse, it isn't doing what you want because you haven't told 
> it what to do with the arguments.
Sorry to cause confusion here. I don't know there is a Pypi project with the same name infix2postfix.py:-(

Nevertheless, Is there anyway to make parse_args works?
>>> parser.parse_args("-4^2+5.3*abs(-2-1)/2")