Python's super() considered super!

[Duncan Booth]

Steven D'Aprano <steve+comp.lang.python at pearwood.info> wrote:

> I was thrilled to learn a new trick, popping keyword arguments before 
> calling super, and wondered why I hadn't thought of that myself. How on 
> earth did I fail to realise that a kwarg dict was mutable and therefore 
> you can remove keyword args, or inject new ones in?
> 
Probably because most of the time it is better to avoid mutating kwargs. 
Instead of popping an argument you simply declare it as a named argument in 
the method signature. Instead of injecting new ones you can pass them as 
named arguments.


def foo(x=None, **kwargs):
	bar(y=2, **kwargs)

	
def bar(**kwargs):
	print(kwargs)

>>> foo(x=1, z=3)
{'y': 2, 'z': 3}
>>> foo(x=1, y=2, z=3)
Traceback (most recent call last):
  File "<pyshell#8>", line 1, in <module>
    foo(x=1, y=2, z=3)
  File "<pyshell#4>", line 2, in foo
    bar(y=2, **kwargs)
TypeError: bar() got multiple values for keyword argument 'y'

-- 
Duncan Booth http://kupuguy.blogspot.com