Terry Reedy wrote:
> On 5/2/2015 6:29 PM, Cecil Westerhof wrote:
>
>> At the moment I define the test functionality in the following way:
>
> Any automated testing is better than none. For idlelib, I use unittest.
> For an individual project with specialized needs, I use a custom test
> framework tuned to those needs.
>
>> else:
>> action = options[0][0]
>> if action == '--all':
>> do_all = True
>> elif action == '--factorial':
>> do_factorial = True
>> elif action == '--fibonacci':
>> do_fibonacci = True
>> elif action == '--happy':
>> do_happy = True
>> elif action == '--lucky':
>> do_lucky = True
>> else:
>> print >> sys.stderr, progname + ': Unhandled parameter '
>> + action sys.exit(1)
>
> There is usually a way to factor out the duplication of repetitive code
> like this.
> Often, a dict is somehow involved.
That cannot be stressed enough. In Python if you test against multiple
constant values you should always consider a dict-based approach.
Also, you should not shy away from using functions as variables. Instead of
do_lucky = True
...
if do_lucky:
do_lucky_func()
you can often write something more direct
action = do_lucky_func
...
action_func()
> I believe the following
> is equivalent to the above.
>
> else:
> action = options[0][0]
> try:
> globals()['do_'+action[2:]] = True
> except KeyError:
> print >> sys.stderr, progname + ': Unhandled parameter ' + action
> sys.exit(1)
To go a bit farther down that path of using naming conventions, dict instead
of extensive if ... elif ... and functions instead of flags here's a
complete implementation with argparse:
$ python3 choose_action.py -h
usage: choose_action.py [-h] [{all,fibonacci,factorial}]
positional arguments:
{all,fibonacci,factorial}
Known actions: all, fibonacci, factorial
optional arguments:
-h, --help show this help message and exit
$ python3 choose_action.py all
fibonacci
factorial
$ python3 choose_action.py
factorial
fibonacci
$ python3 choose_action.py fibonacci
fibonacci
$ python3 choose_action.py non-existent
usage: choose_action.py [-h] [{all,factorial,fibonacci}]
choose_action.py: error: argument action: invalid choice: 'non-existent'
(choose from 'all', 'factorial', 'fibonacci')
$ cat choose_action.py
import argparse
def do_factorial():
print("factorial")
# ...
def do_fibonacci():
print("fibonacci")
# ...
def do_all():
for name, action in lookup.items():
if name != "all":
action()
lookup = {
name[3:]: func
for name, func in globals().items()
if name.startswith("do_")
}
if __name__ == "__main__":
parser = argparse.ArgumentParser()
parser.add_argument(
"action",
nargs="?",
default="all",
choices=lookup,
help="Known actions: %(choices)s")
args = parser.parse_args()
lookup[args.action]()
$
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