variants 0.2.0

variants是一个库，提供创建函数和其他可调用对象的替代形式的语法糖，就像替代构造函数是提供构造函数函数替代形式的类方法一样。

要创建具有变体的函数，只需用@variants.primary装饰主要形式，然后它将.variant装饰器添加到原始函数中，可用于注册新变体。以下是一个简单的函数示例，该函数打印文本，具有指定要打印的文本来源的变体

import variants

@variants.primary
def print_text(txt):
    print(txt)

@print_text.variant('from_file')
def print_text(fobj):
    print_text(fobj.read())

@print_text.variant('from_filepath')
def print_text(fpath):
    with open(fpath, 'r') as f:
        print_text.from_file(f)

@print_text.variant('from_url')
def print_text(url):
    import requests
    r = requests.get(url)
    print_text(r.text)

print_text及其变体可以这样使用

print_text('Hello, world!')                 # Hello, world!

# Create a text file
with open('hello_world.txt', 'w') as f:
    f.write('Hello, world (from file)')

# Print from an open file object
with open('hello_world.txt', 'r') as f:
    print_text.from_file(f)                 # Hello, world (from file)

# Print from the path to a file object
print_text.from_filepath('hello_world.txt') # Hello, world (from file)

# Print from a URL
hw_url = 'https://ganssle.io/files/hello_world.txt'
print_text.from_url(hw_url)                 # Hello, world! (from url)

@variants.primary
@singledispatch
def add(x, y):
    return x + y

@add.variant('from_list')
@add.register(list)
def add(x, y):
    return x + [y]

>>> add(1, 2)
3
>>> add([1], 2)
[1, 2]

>>> add.from_list([1], 2)
[1, 2]
>>> add.from_list()
      7 @add.register(list)
      8 def add(x, y):
----> 9     return x + [y]

TypeError: unsupported operand type(s) for +: 'int' and 'list'

$ pip install variants