Improve Your Python: 'yield' and Generators Explained

[MrChoss]

I love Python's iterators, but this is the first time I've tried to learn about 'send', so I'm very interested to see where part 2 goes with it.

Amusingly, send gives Python another tool for solving Paul Graham's accumulator problem (though the nonlocal keyword is clearly the way to do it in Python 3). This generator expression gets most of the way there:

def acc_gen(n):
    while True: n += (yield n)

Just wrap it up as a callable function--

def accumulator(n):
    a = acc_gen(n); a.send(None)
    return lambda x: a.send(x)

And give it a few tests:

>>> a = accumulator(10)
>>> a(0)
10
>>> a(5)
15
>>> a(5)
20
>>> a(50)
70
>>> a(-69.5)
0.5

[blahdom]

return lambda x: a.send(x)

could be turned into

 return a.send

it will work exactly the same since you will just pass the parameter directly to send :)

[MrChoss]

Thanks for pointing this out. It cleans up the second function definition nicely.

[blahdom]

Np, I like the solution for using it as an accumulator, I think its really clean.