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Composing namedtuple from namedtuples

Published: 2017-11-02

The problem:

One namedtuples is great, two better. But how do I combine the two namedtuples to get the best nametuple of all?

For example, how to combine the Square class with Color class?

Square = namedtuple('Square', 'x0 y0 x1 y1')
Color = namedtuple('Color', 'r g b')
# The opposite of DRY principle - WET (we enjoy typing) principle
ColoredSquare = namedtupe('ColoredSquare', 'x0 y0 x1 y1 r g b')

I don’t like this solution, because there are clearly something to reuse in Square and Color , and also, it isn’t fun to call ColoredSquare ‘s init function that has 7 arguments. The alternative might be writing a custom class that takes Square and Color as arguments of the init function, but then we lost all the benefits from using namedtuples. (TODO add a link of something to support this statement.)

So, here’s the recipe:

class ColoredSquare(namedtuple('ColoredSquare',
                               Square._fields + Color._fields)):
    def from_(cls, square: Square, color: Color):
        return cls(*square, *color)

my_square = ColoredSquare.from_(
        square=Square(0, 0, 1, 1), 
        color=Color(100, 100, 100))

>>> my_square
ColoredSquare(x0=0, y0=0, x1=1, y1=1, r=100, g=100, b=100)

Let me know what you think! Please share or like this post if you think it’s helpful!

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