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

[Jach Feng]

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