python: union keys from multiple dictionary?

Question

I have 5 dictionaries and I want a union of their keys.

alldict =  [dict1, dict2, dict3, dict4, dict5]

I tried

allkey = reduce(         


        

Answer 1

Just one more way, 'cause what the hay:

a={}; [ a.update(b) for b in alldict ] and a.keys()

or the slightly-more-mysterious

reduce(lambda a, b: a.update(b) or a, alldict, {}).keys()

(I'm bummed that there's no built-in function equivalent to

def f(a,b):
   r = {}
   r.update(a)
   r.update(b)
   return r

is there?)