Re: evaluation question
On 30/01/23 10:41 pm, mutt...@dastardlyhq.com wrote: What was the point of the upheaval of converting the print command in python 2 into a function in python 3 if as a function print() doesn't return anything useful? It was made a function because there's no good reason for it to have special syntax in the language. Functions don't need to return things to justify their existence, and in fact the usual convention is that functions whose purpose is to have an effect just return None. -- Greg -- https://mail.python.org/mailman/listinfo/python-list
Re: Custom help format for a choice argparse argument
On 27/01/2023 21:31, Ivan "Rambius" Ivanov wrote:
Hello,
I am developing a script that accepts a time zone as an option. The
time zone can be any from pytz.all_timezones. I have
def main():
parser = argparse.ArgumentParser()
parser.add_argument("-z", "--zone", choices=pytz.all_timezones)
args = parser.parse_args()
print(args)
print(f"Specified timezone: {args.zone}")
It works, but when I run it with the -h option it dumps all entries in
pytz.all_timezones. I would like to modify the help format for just
-z|--zone option. I read the docs about HelpFormatter and argparse.py
and I ended up with
class CustomHelpFormatter(argparse.HelpFormatter):
def _metavar_formatter(self, action, default_metavar):
if action.dest == 'zone':
result = 'zone from pytz.all_timezones'
def format(tuple_size):
if isinstance(result, tuple):
return result
else:
return (result, ) * tuple_size
return format
else:
return super(CustomHelpFormatter,
self)._metavar_formatter(action, default_metavar)
def main():
parser = argparse.ArgumentParser(formatter_class=CustomHelpFormatter)
parser.add_argument("-z", "--zone", choices=pytz.all_timezones)
args = parser.parse_args()
print(args)
print(f"Specified timezone: {args.zone}")
This works, but is there a more elegant way to achieve it?
It may be sufficient to specify a metavar:
>>> import argparse
>>> p = argparse.ArgumentParser()
>>> p.add_argument("--foo", choices="alpha beta gamma".split(),
metavar="")
[...]
>>> p.parse_args(["-h"])
usage: [-h] [--foo ]
optional arguments:
-h, --helpshow this help message and exit
--foo
While that helps with --help it doesn't always prevent the choices list
from being spelt out:
>>> p.parse_args(["--foo", "whatever"])
usage: [-h] [--foo ]
: error: argument --foo: invalid choice: 'whatever' (choose from
'alpha', 'beta', 'gamma')
--
https://mail.python.org/mailman/listinfo/python-list
Re: evaluation question
On 30/01/2023 09:41, mutt...@dastardlyhq.com wrote:
On Sun, 29 Jan 2023 23:57:51 -0500
Thomas Passin wrote:
On 1/29/2023 4:15 PM, elvis-85...@notatla.org.uk wrote:
On 2023-01-28, Louis Krupp wrote:
On 1/27/2023 9:37 AM, mutt...@dastardlyhq.com wrote:
eval("print(123)")
123
Does OP expect the text to come from the eval or from the print?
x = print( [i for i in range(1, 10)] )
[1, 2, 3, 4, 5, 6, 7, 8, 9]
x
(nothing printed)
Because print() returns nothing (i.e., the statement x is None is True).
I don't understand this. What was the point of the upheaval of converting
the print command in python 2 into a function in python 3 if as a function
print() doesn't return anything useful? Surely even the length of the
formatted string as per C's sprintf() function would be helpful?
That's a fair question, or rather 2 fair questions.
There is an explanation of why the change was made at
https://snarky.ca/why-print-became-a-function-in-python-3/
In brief: (a) the print() function is more flexible and can be used in
expressions
(b) Python's syntax was simplified by dropping the
special syntax used by the print statement.
sys.stdout.write() does return the number of characters output (you
could use this instead of print() if you need this;
remember to add a '\n' character at the end of a line). I guess the option
of making print() do the same either was not considered, or was
rejected, when print was made a function.
Best wishes
Rob Cliffe
--
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Re: evaluation question
On Sun, 29 Jan 2023 23:57:51 -0500
Thomas Passin wrote:
>On 1/29/2023 4:15 PM, elvis-85...@notatla.org.uk wrote:
>> On 2023-01-28, Louis Krupp wrote:
>>> On 1/27/2023 9:37 AM, mutt...@dastardlyhq.com wrote:
>>
>>
>>> eval("print(123)")
123
>>
>>
>> Does OP expect the text to come from the eval or from the print?
>>
> x = print( [i for i in range(1, 10)] )
>> [1, 2, 3, 4, 5, 6, 7, 8, 9]
>>
> x
>> (nothing printed)
>
>Because print() returns nothing (i.e., the statement x is None is True).
I don't understand this. What was the point of the upheaval of converting
the print command in python 2 into a function in python 3 if as a function
print() doesn't return anything useful? Surely even the length of the
formatted string as per C's sprintf() function would be helpful?
--
https://mail.python.org/mailman/listinfo/python-list
Re: Usenet vs. Mailing-list
On 2023-01-28, Dennis Lee Bieber wrote: > On Sat, 28 Jan 2023 20:07:44 +, Chris Green declaimed the > following: > > >>As far as I am aware the mirroring of the Python mailing list on >>comp.lan.python works perfectly. I love gmane! :-) > > Is gmane's gmane.comp.python.general allowing posts to go through > again? I had to revert to comp.lang.python some time back when gmane kept > rejecting outgoing posts. No. FWIW, it's the mailing list that's blocking them, not Gmane. That's why I wrote this: https://github.com/GrantEdwards/hybrid-inews It's an inews work-alike that submits most posts via gmanes NNTP server, but will deal with particular groups (e.g. gmane.comp.python.general) that want posts submitted via email. It allows me to continue to read (and post to) the Python mailling list via slrn pointed at gmane. It is, of course, written in Python. -- https://mail.python.org/mailman/listinfo/python-list
Re: Usenet vs. Mailing-list
On 2023-01-28, Chris Green wrote: > As far as I am aware the mirroring of the Python mailing list on > comp.lan.python works perfectly. I love gmane! :-) If gmane stopped working, I'd have to retire and give up on computers. I supposed I might be able to hammer procmail and mutt into something tolerable, but slrn pointed at gmane works wonderfully without any futzing. NNTP and newsreaders are designed specifically for the task to which people have coopted e-mail into via mailing lists. -- Grant -- https://mail.python.org/mailman/listinfo/python-list
