On 25Jan2023 16:15, Chris Angelico <ros...@gmail.com> wrote:
On Wed, 25 Jan 2023 at 14:42, Jach Feng <jf...@ms4.hinet.net> wrote:
I was happy working with argparse during implement my script. To save the
typing, I used a default equation for testing.
Sure, but what benefit was it bringing you? Just the usage (help)
message? Did you have many options to handle?
sample = "-4^2+5.3*abs(-2-1)/2, abs(Abc)*(B+C)/D, (-3) * sqrt(1-(x1/7)*(y1/7)) *
sqrt(abs((x0-4.5)/(y0-4)))"
parser = argparse.ArgumentParser(description='Convert infix notation to
postfix')
parser.add_argument('infix', nargs='?', default=sample, help="....")
If this was the whole thing, I don't see what argparse was doing for you
which was better than just handling the arguments yourself - there's
only one after all.
You're still not really using argparse as an argument parser. Why not
just do your own -h checking? Stop trying to use argparse for what
it's not designed for, and then wondering why it isn't doing what you
expect it to magically know.
I'm with Chris here.
As someone who pretty well _never_ uses argparse, and occasionally uses
getopt, I'd do something like this:
usage = '''Usage: infix
Parse the argument infix as an expression, print the result.'''
badopts = False
cmd = argv.pop(0)
if not argv:
print(f'{cmd}: missing infix argument', file=sys.stderr)
badopts = True
else:
infix = argv.pop(0)
if infix in ('-h', '--help'):
print(usage)
exit(0)
if argv:
print(f'{cmd}: extra arguments after infix: {argv!r}',
file=sys.stderr)
badopts = True
if badopts:
print(usage, file=sys.stderr)
exit(2)
... work with infix as desired ...
This:
- avoids trying to shoehorn argparse into behaving in a way it was not
designed for
- avoids users needing to know the standard UNIX/POSIX "--" idiom for
marking off the end of options
- supports a -h or --help leading option
Cheers,
Cameron Simpson <c...@cskk.id.au>
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