python模块之argparse--参数解析

一、简介：

argparse是python用于解析命令行参数和选项的标准模块，用于代替已经过时的optparse模块。argparse模块的作用是用于 解析命令行参数，例如python parseTest.py input.txt output.txt --user=name --port=8080。

二、使用步骤：

1：import argparse

2：parser = argparse.ArgumentParser()

3：parser.add_argument()

4：parser.parse_args()

解释：首先导入该模块；然后创建一个解析对象；然后向该对象中添加你要关注的命令行参数和选项，每一个add_argument方法对应一个你要关注的参数或选项；最后调用parse_args()方法进行解析；解析成功之后即可使用，下面简单说明一下步骤2和3。

三、方法ArgumentParser(prog=None, usage=None,description=None, epilog=None, parents=[],formatter_class=argparse.HelpFormatter, prefix_chars='-',fromfile_prefix_chars=None, argument_default=None,conflict_handler='error', add_help=True)

这些参数都有默认值，当调用parser.print_help()或者运行程序时由于参数不正确(此时python解释器其实也是调用了pring_help()方法)时，会打印这些描述信息，一般只需要传递description参数，如上。

四、方法add_argument(name or flags...[, action][, nargs][, const][, default][, type][, choices][, required][, help][, metavar][, dest])

其中：

name or flags：命令行参数名或者选项，如上面的address或者-p,--port.其中命令行参数如果没给定，且没有设置defualt，则出错。但是如果是选项的话，则设置为None

nargs：命令行参数的个数，一般使用通配符表示，其中，'?'表示只用一个，'*'表示0到多个，'+'表示至少一个

default：默认值

type：参数的类型，默认是字符串string类型，还有float、int等类型

help：和ArgumentParser方法中的参数作用相似，出现的场合也一致

import argparse

def parse_args():
    description = usage: %prog [options] poetry-file

This is the Slow Poetry Server, blocking edition.
Run it like this:

  python slowpoetry.py 

If you are in the base directory of the twisted-intro package,
you could run it like this:

  python blocking-server/slowpoetry.py poetry/ecstasy.txt

to serve up John Donne's Ecstasy, which I know you want to do.


    parser = argparse.ArgumentParser(description = description)
    
    help = The addresses to connect.
    parser.add_argument('addresses',nargs = '*',help = help)

    help = The filename to operate on.Default is poetry/ecstasy.txt
    parser.add_argument('filename',help=help)

    help = The port to listen on. Default to a random available port.
    parser.add_argument('-p',--port', type=int, help=help)

    help = The interface to listen on. Default is localhost.
    parser.add_argument('--iface', help=help, default='localhost')

    help = The number of seconds between sending bytes.
    parser.add_argument('--delay', type=float, help=help, default=.7)

    help = The number of bytes to send at a time.
    parser.add_argument('--bytes', type=int, help=help, default=10)

    args = parser.parse_args();
    return args

if __name__ == '__main__':
    args = parse_args()
    
    for address in args.addresses:
        print 'The address is : %s .' % address
    
    print 'The filename is : %s .' % args.filename
    print 'The port is : %d.' % args.port
    print 'The interface is : %s.' % args.iface
    print 'The number of seconds between sending bytes : %f'% args.delay
    print 'The number of bytes to send at a time : %d.' % args.bytes

运行该脚本：python test.py --port 10000 --delay 1.2 127.0.0.1 172.16.55.67 poetry/ecstasy.txt

输出为：

The address is : 127.0.0.1 .
The address is : 172.16.55.67 .
The filename is : poetry/ecstasy.txt .
The port is : 10000.
The interface is : localhost.
The number of seconds between sending bytes : 1.200000
The number of bytes to send at a time : 10.