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.
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