Python 中的参数解析（必需与可选）

我目前正在编写一个能够采用多个标志的脚本。我希望它无论最后一个参数是什么都应该是“start|stop|status”。

#!/usr/bin/env python

from argparse import ArgumentParser


def argument_analysis():
    """
This will analyze arguments, and return the region as a string, the filter as a dictionary, and the command as a string.
    :return: region,filters,command
    """
    parser_options = ArgumentParser()
    parser_options.add_argument("-r", "--region", dest='region',
                                help="Filter by region.")
    parser_options.add_argument("-n", "--name", dest='name',
                                help="Filter by hostname.")
    parser_options.add_argument("-P", "--project", dest='project',
                                help="Filter by Project tag.")
    parser_options.add_argument("-U", "--usage", dest='usage',
                                help="Filter by Usage tag.")
    parser_options.add_argument("-i", "--instance_id", dest='instance_id',
                                help="Filter by instance_id.")
    parser_options.add_argument("-t", "--type", dest='type',
                                help="Filter by instance_size.")
    parser_options.add_argument("-p", "--ip", dest='internal_ip',
                                help="Filter by internal_ip")
    parser_options.add_argument("-c", "--command", dest='command',
                                help="stop/start, or check the status of instances.")
    parser_options.add_argument("-a", "--all", dest='all', default=False, action='store_true',
                                help="No filter, display status of all servers.")
    arguments = vars(parser_options.parse_args())
    return arguments


if __name__ == '__main__':
    print argument_analysis()

我想要它，以便 ./argument_analysis_script.py 最后需要一个“停止|开始|状态”。我没有太多运气获得 ARgumentParser() 的帮助。如果有人有任何建议，那将非常有帮助。

在此先感谢您的时间。

注意：如果未输入 [stop|start|restart|status]，我希望脚本停止，并解释需要 [stop|start|restart|status]。

**更新** **更新** **更新**

经过更多挖掘后，为了能够分析/使用命令行选项和参数，我偶然发现了 OptionParser，我避免使用它docs.python.org http://docs.python.org说它是已弃用 https://docs.python.org/2/library/optparse.html。不管怎样，因为这是我能找到的唯一能给我真正想要的东西，这里是我所得到的更新：

#!/usr/bin/env python

from optparse import OptionParser


def argument_analysis():
    """
This will analyze arguments, and return the region as a string, the filter as a dictionary, and the command as a string.
    :return: region,filters,command
    """
    parser = OptionParser()
    parser.add_option("-r", "--region", dest='region',
                      help="Filter by region.")
    parser.add_option("-n", "--name", dest='name',
                      help="Filter by hostname.")
    parser.add_option("-P", "--project", dest='project',
                      help="Filter by Project tag.")
    parser.add_option("-U", "--usage", dest='usage',
                      help="Filter by Usage tag.")
    parser.add_option("-i", "--instance_id", dest='instance_id',
                      help="Filter by instance_id.")
    parser.add_option("-t", "--type", dest='type',
                      help="Filter by instance_size.")
    parser.add_option("-p", "--ip", dest='internal_ip',
                      help="Filter by internal_ip")
    parser.add_option("-c", "--command", dest='command',
                      help="stop/start, or check the status of instances.")
    parser.add_option("-a", "--all", dest='all', default=False, action='store_true',
                      help="No filter, display status of all servers.")
    (options, args) = parser.parse_args()  # Grab Options specifed from above, as well as actual Arguments.

    options = vars(options)  # Convert 'options' into dictionary: key=dest_name, value=dest_value

    # Getting variables for dictionary below.
    region_filter = options['region']
    name_filter = options['name']
    project_filter = options['project']
    usage_filter = options['usage']
    instance_filter = options['instance_id']
    type_filter = options['type']
    ip_filter = options['internal_ip']
    all_filter = options['all']

    region = region_filter if region_filter else 'us-east-1' # Return 'us-east-1' region is not specified.

    filters = {'tag:Name': name_filter, 'tag:Project': project_filter, 'tag:Usage': usage_filter,
               'instance-id': instance_filter, 'instance_type': type_filter, 'private-ip-address': ip_filter,
               'all': all_filter}

    command = 'No commands.' if not args else args  #Return "No commands" if no command is specified.

    return region, filters, command


if __name__ == '__main__':
    opts_and_args = argument_analysis()
    print "Region: " + str(opts_and_args[0])
    print "Filters: " + str(opts_and_args[1])
    print "Command: " + str(opts_and_args[2])

正如您所看到的，您可以根据返回的对象或定义应用您想要的任何逻辑。感谢大家对这一问题的帮助。

也许你可以使用 argparse 来做到这一点，但另一种选择是使用sys module

import sys
print sys.argv # prints command line arguments

sys.argv在列表中包含命令行参数，因此您可以检查最后一个参数：

if sys.argv[-1] != 'start':
    print "Error, expected <something>"
    // quit