Python怎么自动判断输入参数类型

直接通过装饰器@typic.al，然后自动根据 Python3 的注解功能自动判断输入参数类型。

示例：

>>> import typic
>>>
>>> @typic.al
>>> def multi(a: int, b: int):
...    return a * b
...
>>> multi('2', '3')
6

>>> class DuckRegistry:
...     """A Registry for all the ducks"""
...
...     @typic.al
...     def __init__(self, *duck: Duck):
...         self._reg = {x.name: x for x in duck}
...
...     @typic.al
...     def add(self, duck: Duck):
...         self._reg[duck.name] = duck
...
...     @typic.al
...     def find(self, name: str):
...         """Try to find a duck by its name. Otherwise, try with type."""
...         if name not in self._reg:
...             matches = [x for x in self._reg.values() if x.type == name]
...             if matches:
...                 return matches[-1] if len(matches) == 1 else matches
...         return self._reg[name]
...
>>> registry = DuckRegistry({'type': 'black', 'name': 'Daffy'})
>>> registry.find('Daffy')
Duck(type=<DuckType.BLK: 'black'>, name='Daffy')
>>> registry.add({'type': 'white', 'name': 'Donald'})
>>> registry.find('Donald')
Duck(type=<DuckType.WHT: 'white'>, name='Donald')

>>> registry.add({'type': 'goose', 'name': 'Maynard'})
Traceback (most recent call last):
 ...
ValueError: 'goose' is not a valid DuckType

Python 让使用 ffmpeg 处理视频文件变得更简单，比如把

ffmpeg -i input.mp4 -i overlay.png -filter_complex "[0]trim=start_frame=10:end_frame=20[v0];\
    [0]trim=start_frame=30:end_frame=40[v1];[v0][v1]concat=n=2[v2];[1]hflip[v3];\
    [v2][v3]overlay=eof_action=repeat[v4];[v4]drawbox=50:50:120:120:red:t=5[v5]"\
    -map [v5] output.mp4

变为：

import ffmpeg

in_file = ffmpeg.input('input.mp4')
overlay_file = ffmpeg.input('overlay.png')
(
    ffmpeg
    .concat(
        in_file.trim(start_frame=10, end_frame=20),
        in_file.trim(start_frame=30, end_frame=40),
    )
    .overlay(overlay_file.hflip())
    .drawbox(50, 50, 120, 120, color='red', thickness=5)
    .output('out.mp4')
    .run()
)