サードパーティのdocoptライブラリを使い、ユーザーがコマンドラインに入力した偶数を合計するPythonプログラムを紹介しよう：

``` python
"""Sum Even.

Usage: sum_even <number>...
"""
from docopt import docopt


def sum_even(numbers):
    """Sum all the even numbers in a list."""
    assert isinstance(numbers, list), "numbers must be a list"

    total = 0
    for n in numbers:
        try:
            n_flt = float(n)
            if n_flt % 2 == 0:
                total += int(n_flt)  # it's an int if it's even, and python ints can be much larger than floats
        except ValueError:
            return f"{n} is not a number"
    return total


if __name__ == "__main__":
    arguments = docopt(__doc__, version='Sum All v1.0')

    numbers = arguments['<number>']
    try:
        print(sum_even(numbers))
    except Exception as e:
        print(f"Could not sum all even numbers:\n {e}")
```

Docoptをインストールするには
```
pip install docopt
```

プログラムは
```
python sum_even.py 1 2 3 4.0 4.1 1e3
```

しかし、floatが変換するようなinfやnanを処理する特別なコードはない。その代わり、%2の後に0が来ないので、それらをスキップするだけである。

また、単にsum_evenを呼び出すのではなく、pythonを呼び出す必要があります。適切なセットアップファイルを作成し、pipでインストールすることで、独自のコマンドライン引数にすることができます。
Here's a python program that uses the third-party docopt library to sum all the even numbers the user enters in a command line:

``` python
"""Sum Even.

Usage: sum_even <number>...
"""
from docopt import docopt


def sum_even(numbers):
    """Sum all the even numbers in a list."""
    assert isinstance(numbers, list), "numbers must be a list"

    total = 0
    for n in numbers:
        try:
            n_flt = float(n)
            if n_flt % 2 == 0:
                total += int(n_flt)  # it's an int if it's even, and python ints can be much larger than floats
        except ValueError:
            return f"{n} is not a number"
    return total


if __name__ == "__main__":
    arguments = docopt(__doc__, version='Sum All v1.0')

    numbers = arguments['<number>']
    try:
        print(sum_even(numbers))
    except Exception as e:
        print(f"Could not sum all even numbers:\n {e}")
```

Docopt can be installed with:
```
pip install docopt
```

The program can then be run with:
```
python sum_even.py 1 2 3 4.0 4.1 1e3
```

However, it doesn't have any specific code for handling inf or nan, which float would convert. It instead just skips those because they don't result in 0 after the %2.

It also requires a call to python instead of just calling sum_even. It's possible to make it its own command line argument by making the right setup file and pip installing it.