Python: Can optparse have the ACTION attribute to act both like STORE and STORE_TRUE?

问题:

I am using optparse to get command line input.

Lets say that I am running a script demo.py and it creates some output. But unless I specify the command line input, the output is not written to a file.

I am trying to do the following:

python demo.py in command line should run the script, but not write the output anywhere.

python demo.py -o in command line should write the output to my default file name output.txt.

python demo.py -o demooutput.txt in command line should write the output to file demooutput.txt.

PS: I would not prefer to switch to argparse from optparse.

回答1:

You can use optparse-callbacks to achieve this.

Here is how it wiill work for your use case.

parser.add_option("-o", action="callback", dest="output", callback=my_callback)  def my_callback(option, opt, value, parser):      if len(parser.rargs) > 0:          next_arg = parser.rargs[0]          if not next_arg.startswith("-"):              # Next argument is not another option              del parser.rargs[0]              setattr(parser.values, option.dest, next_arg)              return      # If not processed, set the default value      setattr(parser.values, option.dest, "output.txt") 

回答2:

I don't think there is unfortunately - the only way I can think of is hacking around the problem by adding your own logic statements. The following code should do the trick.

import re, sys import optparse from OptionParser     usage = "usage: %prog [options] arg" parser = OptionParser(usage) if '-f' in argv:     a = argv.index('-f')     if (a != len(argv)-1) and re.search('[.]txt', argv[a+1]):         parser.add_option("-f", "--foo", dest="foo")     else:         parser.add_option("-f", dest="foo", action="store_true") 

回答3:

This doesn't answer the direct question, 'how to define an Action...', but it handles the inputs in a simple way.

Set '-o' to be 'store_true'. If True check the 'args' variable for a file name.

(options, args) = parser.parse_args() if options.o:     if args:         dest = args[0]     else:         dest = 'output.txt' else:     dest = '' 

(In argparse the equivalent would be to define a positional argument with nargs='?'.)

If these are the only arguments, you could also get by with checking for the filename without requiring the `-o'.

Another possibility - 'store_const', with the positional 'filename' having priority:

parser = optparse.OptionParser() parser.add_option('-o',dest='dest',action='store_const', const='output.txt', default='') (options, args) = parser.parse_args() if args:     options.dest = args[0] print options 

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