轻量级命令行参数默认值

尽管argparse很棒，并且是完整文档化的命令行开关和高级特性的正确答案，但是您可以使用函数参数默认值非常简单地处理直接的位置参数。

import sys

def get_args(name='default', first='a', second=2):
    return first, int(second)

first, second = get_args(*sys.argv)
print first, second

'name'参数捕获脚本名称，但不使用。测试输出如下所示:

> ./test.py
a 2
> ./test.py A
A 2
> ./test.py A 20
A 20

对于只想要一些默认值的简单脚本，我发现这已经足够了。您可能还希望在返回值中包含一些类型强制，否则命令行值将全部为字符串。

我更喜欢optparse而不是getopt。它非常具有声明性:您告诉它选项的名称和它们应该具有的效果(例如，设置一个布尔字段)，它会返回给您一个根据您的规范填充的字典。

http://docs.python.org/lib/module-optparse.html

值得一提的是主机游戏。它很容易使用。看看吧:

from consoleargs import command

@command
def main(url, name=None):
  """
  :param url: Remote URL 
  :param name: File name
  """
  print """Downloading url '%r' into file '%r'""" % (url, name)

if __name__ == '__main__':
  main()

现在在控制台:

% python demo.py --help
Usage: demo.py URL [OPTIONS]

URL:    Remote URL 

Options:
    --name -n   File name

% python demo.py http://www.google.com/
Downloading url ''http://www.google.com/'' into file 'None'

% python demo.py http://www.google.com/ --name=index.html
Downloading url ''http://www.google.com/'' into file ''index.html''

以防万一，如果你需要在Win32 (2K, XP等)上获取unicode参数，这可能会有所帮助:

from ctypes import *

def wmain(argc, argv):
    print argc
    for i in argv:
        print i
    return 0

def startup():
    size = c_int()
    ptr = windll.shell32.CommandLineToArgvW(windll.kernel32.GetCommandLineW(), byref(size))
    ref = c_wchar_p * size.value
    raw = ref.from_address(ptr)
    args = [arg for arg in raw]
    windll.kernel32.LocalFree(ptr)
    exit(wmain(len(args), args))
startup()

我扩展了Erco的方法，允许使用必需的位置参数和可选参数。这些参数应该在-d， -v等参数之前。

位置参数和可选参数可以分别用PosArg(i)和OptArg(i, default)检索。 当找到一个可选参数时，搜索选项的起始位置(例如-i)将向前移动1，以避免导致“意外”致命。

import os,sys


def HelpAndExit():
    print("<<your help output goes here>>")
    sys.exit(1)

def Fatal(msg):
    sys.stderr.write("%s: %s\n" % (os.path.basename(sys.argv[0]), msg))
    sys.exit(1)

def NextArg(i):
    '''Return the next command line argument (if there is one)'''
    if ((i+1) >= len(sys.argv)):
        Fatal("'%s' expected an argument" % sys.argv[i])
    return(1, sys.argv[i+1])

def PosArg(i):
    '''Return positional argument'''
    if i >= len(sys.argv):
        Fatal("'%s' expected an argument" % sys.argv[i])
    return sys.argv[i]

def OptArg(i, default):
    '''Return optional argument (if there is one)'''
    if i >= len(sys.argv):
        Fatal("'%s' expected an argument" % sys.argv[i])
    if sys.argv[i][:1] != '-':
        return True, sys.argv[i]
    else:
        return False, default


### MAIN
if __name__=='__main__':

    verbose = 0
    debug   = 0
    infile  = "infile"
    outfile = "outfile"
    options_start = 3

    # --- Parse two positional parameters ---
    n1 = int(PosArg(1))
    n2 = int(PosArg(2))

    # --- Parse an optional parameters ---
    present, a3 = OptArg(3,50)
    n3 = int(a3)
    options_start += int(present)

    # --- Parse rest of command line ---
    skip = 0
    for i in range(options_start, len(sys.argv)):
        if not skip:
            if   sys.argv[i][:2] == "-d": debug ^= 1
            elif sys.argv[i][:2] == "-v": verbose ^= 1
            elif sys.argv[i][:2] == "-i": (skip,infile)  = NextArg(i)
            elif sys.argv[i][:2] == "-o": (skip,outfile) = NextArg(i)
            elif sys.argv[i][:2] == "-h": HelpAndExit()
            elif sys.argv[i][:1] == "-":  Fatal("'%s' unknown argument" % sys.argv[i])
            else:                         Fatal("'%s' unexpected" % sys.argv[i])
        else: skip = 0

    print("Number 1 = %d" % n1)
    print("Number 2 = %d" % n2)
    print("Number 3 = %d" % n3)
    print("Debug    = %d" % debug)
    print("verbose  = %d" % verbose)
    print("infile   = %s" % infile)
    print("outfile  = %s" % outfile) 

我更喜欢点击。它抽象了管理选项，并允许“(…)以一种可组合的方式，用尽可能少的代码创建漂亮的命令行界面”。

下面是用法示例:

import click

@click.command()
@click.option('--count', default=1, help='Number of greetings.')
@click.option('--name', prompt='Your name',
              help='The person to greet.')
def hello(count, name):
    """Simple program that greets NAME for a total of COUNT times."""
    for x in range(count):
        click.echo('Hello %s!' % name)

if __name__ == '__main__':
    hello()

它还会自动生成格式良好的帮助页面:

$ python hello.py --help
Usage: hello.py [OPTIONS]

  Simple program that greets NAME for a total of COUNT times.

Options:
  --count INTEGER  Number of greetings.
  --name TEXT      The person to greet.
  --help           Show this message and exit.