variants 0.1.0

variants is a library that provides syntactic sugar for creating alternate forms of functions and other callables, in the same way that alternate constructors are class methods that provide alternate forms of the constructor function.

To create a function with variants, simply decorate the primary form with @variants.primary, which then adds the .variant decorator to the original function, which can be used to register new variants. Here is a simple example of a function that prints text, with variants that specify the source of the text to print:

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 and its variants can be used as such:

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