What's the best way to parse command line arguments?
什么是解析Python命令行参数的最简单 ， 最 先进 ，最灵活的方法或库？
This answer suggests optparse which is appropriate for older Python versions. For Python 2.7 and above, argparse replaces optparse . See this answer for more information.
As other people pointed out, you are better off going with optparse over getopt. getopt is pretty much a one-to-one mapping of the standard getopt(3) C library functions, and not very easy to use.
optparse, while being a bit more verbose, is much better structured and simpler to extend later on.
Here's a typical line to add an option to your parser:
parser.add_option('-q', '--query',
action="store", dest="query",
help="query string", default="spam")
It pretty much speaks for itself; at processing time, it will accept -q or --query as options, store the argument in an attribute called query and has a default value if you don't specify it. It is also self-documenting in that you declare the help argument (which will be used when run with -h/--help) right there with the option.
Usually you parse your arguments with:
options, args = parser.parse_args()
This will, by default, parse the standard arguments passed to the script (sys.argv[1:])
options.query will then be set to the value you passed to the script.
You create a parser simply by doing
parser = optparse.OptionParser()
These are all the basics you need. Here's a complete Python script that shows this:
import optparse
parser = optparse.OptionParser()
parser.add_option('-q', '--query',
action="store", dest="query",
help="query string", default="spam")
options, args = parser.parse_args()
print 'Query string:', options.query
5 lines of python that show you the basics.
Save it in sample.py, and run it once with
python sample.py
and once with
python sample.py --query myquery
Beyond that, you will find that optparse is very easy to extend. In one of my projects, I created a Command class which allows you to nest subcommands in a command tree easily. It uses optparse heavily to chain commands together. It's not something I can easily explain in a few lines, but feel free to browse around in my repository for the main class, as well as a class that uses it and the option parser
Other answers do mention that argparse is the way to go for new Python, but do not give usage examples. For completeness, here is a short summary of how to use argparse:
1) Initialize
import argparse
# Instantiate the parser
parser = argparse.ArgumentParser(description='Optional app description')
2) Add Arguments
# Required positional argument
parser.add_argument('pos_arg', type=int,
help='A required integer positional argument')
# Optional positional argument
parser.add_argument('opt_pos_arg', type=int, nargs='?',
help='An optional integer positional argument')
# Optional argument
parser.add_argument('--opt_arg', type=int,
help='An optional integer argument')
# Switch
parser.add_argument('--switch', action='store_true',
help='A boolean switch')
3) Parse
args = parser.parse_args()
4) Access
print("Argument values:")
print(args.pos_arg)
print(args.opt_pos_arg)
print(args.opt_arg)
print(args.switch)
5) Check Values
if args.pos_arg > 10:
parser.error("pos_arg cannot be larger than 10")
Usage
Correct use:
$ ./app 1 2 --opt_arg 3 --switch
Argument values:
1
2
3
True
Incorrect arguments:
$ ./app foo 2 --opt_arg 3 --switch
usage: convert [-h] [--opt_arg OPT_ARG] [--switch] pos_arg [opt_pos_arg]
app: error: argument pos_arg: invalid int value: 'foo'
$ ./app 11 2 --opt_arg 3
Argument values:
11
2
3
False
usage: app [-h] [--opt_arg OPT_ARG] [--switch] pos_arg [opt_pos_arg]
convert: error: pos_arg cannot be larger than 10
Full help:
$ ./app -h
usage: app [-h] [--opt_arg OPT_ARG] [--switch] pos_arg [opt_pos_arg]
Optional app description
positional arguments:
pos_arg A required integer positional argument
opt_pos_arg An optional integer positional argument
optional arguments:
-h, --help show this help message and exit
--opt_arg OPT_ARG An optional integer argument
--switch A boolean switch
Using docopt
Since 2012 Python has a very easy, powerful and really cool module for argument parsing called docopt. It works with Python 2.6 to 3.5 and needs no installation (just copy it). Here is an example taken from it's documentation:
"""Naval Fate.
Usage:
naval_fate.py ship new <name>...
naval_fate.py ship <name> move <x> <y> [--speed=<kn>]
naval_fate.py ship shoot <x> <y>
naval_fate.py mine (set|remove) <x> <y> [--moored | --drifting]
naval_fate.py (-h | --help)
naval_fate.py --version
Options:
-h --help Show this screen.
--version Show version.
--speed=<kn> Speed in knots [default: 10].
--moored Moored (anchored) mine.
--drifting Drifting mine.
"""
from docopt import docopt
if __name__ == '__main__':
arguments = docopt(__doc__, version='Naval Fate 2.0')
print(arguments)
So this is it: 2 lines of code plus your doc string which is essential and you get your arguments parsed and available in your arguments object. I told you it's cool, didn't I ;-)
Using python-fire
Since 2017 python-fire has another cool module which can give a CLI interface to your code with you doing zero argument parsing. Here's a simple example from the documentation (this small program exposes function double to the command line):
import fire
class Calculator(object):
def double(self, number):
return 2 * number
if __name__ == '__main__':
fire.Fire(Calculator)
From the command line, you can run:
> calculator.py double 10
20
> calculator.py double --number=15
30
Awesome ain't it?
链接地址: http://www.djcxy.com/p/30418.html上一篇: 如何解析Java中的命令行参数？
下一篇: 解析命令行参数的最好方法是什么？