如何有效地构造argparse参数中一个，两个或三个选择的选择？

Question

I am designing an argparse-based command line program, and one of the arguments that must be made asks the user to select one or more out of a total of three choices for the format of an output graph. If the user does not mention this argument within the command line, then by default, this argument outputs all three types of the output graphs.

So, the argument itself looks more or less like this:

import argparse

if __name__ == "__main__":
    BobsProgram = argparse.ArgumentParser(prog= "BobsProgram")
    BobsProgram.description= "This code analyzes these inputs, and will output one or more graphs of your choosing."

    BobsProgram.add_argument("-output_graph", choices= ["pie", "bar", "scatter"], default= all, nargs= "+",
    help= "Unless otherwise indicated, the output graphs will be given in the pie, bar, and scatter forms.")

So, after I ran the args= BobsProgram.parse_args() line and started to dispatch my arguments, I wanted it set up so that the user could type in their choices in order they wanted. I have only found it possible to make the command line program function when I set up seven conditional blocks:

if args.output_graph == ["pie"]:
    ##format the output file as a pie chart
elif args.output_graph == ["bar"]:
    ##format the output file as a bar chart
elif args.output_graph == ["scatter"]:
    ##format the output as a scatter chart
elif args.output_graph == ["pie","bar"] and ["bar", "pie"]:
    ##format the output as pie and bar charts
elif args.output_graph == ["pie","scatter"] and ["scatter","pie"]:
    ##format the output as pie and scatter charts
elif args.output_graph == ["bar", "scatter"] and ["scatter","bar"]:
    ##format the output as bar and scatter charts
else:
    ##format the output as bar, pie, and scatter charts

Ultimately, although the code works, it does not seem very Pythonic, as I must replicate a lot of the same code within each conditional block. How can I amend this to make it more efficient?

Answer 1

I'd do something like:

for arg in args.output_graph:
    if arg == 'pie':
        #add_pie_chart()
    if arg == 'bar':
        #add_bar_chart()
    if arg == 'scatter':
        #add_scatter_plot()

The graph functionality now is only called once for each chart. This should work as long as your add chart functions play relatively nice with each other, ie all get added to a master canvas before results are displayed.

Answer 2

If the order doesn't matter then you could do:

alist = args.your_name
if 'foo' in alist:
   # do foo
elif 'bar' in alist:
   # do bar
# etc

If the user provided order matters then the something like this:

for fn in alist:
    if fn in ['foo']:    # or `fn == 'foo'`
        # do foo
    elif fn in ['bar']:
        # do bar