Update list of dictionaries elementwise in Python
Question: Say we have a list of dictionaries in Python:

    
    
    A = [{'x': 1, 'y': 2, 'z': 3},{'x': 0, 'y': 10, 'z': 11}]
    

We pick out the 'x'-values using `map()`

    
    
    x = map((lambda i: i['x']), A)
    

and do something with them. Now, what is the cleanest way to update all the
`'x'`-values of `A` in a comparable way - ie., without using a for-loop?


Answer: 
    >>> r = [{'x': 1, 'y': 2, 'z': 3},{'x': 0, 'y': 10, 'z': 11}]
    >>> r
    [{'y': 2, 'x': 1, 'z': 3}, {'y': 10, 'x': 0, 'z': 11}]
    
    >>> [i.__setitem__('x', 10) for i in r]
    [None, None]
    >>> r
    [{'y': 2, 'x': 10, 'z': 3}, {'y': 10, 'x': 10, 'z': 11}]
    

It's not horrible, but I think a for loop would be nicer. I'd only do this if
'r' were really large and performance is super important.

