I have 5 dictionaries and I want a union of their keys.
alldict = [dict1, dict2, dict3, dict4, dict5]
allkey = reduce(lambda x, y: set(x.keys()).union(y.keys()), alldict)
but it gave me an error
AttributeError: 'set' object has no attribute 'keys'
Am I doing it wrong ? I using normal forloop but I wonder why the above code didn’t work.
Your solution works for the first two elements in the list, but then
dict2 got reduced into a set and that set is put into your lambda as the
x. So now
x does not have the method
The solution is to make x be a set from the very beginning by initializing the reduction with an empty set (which happens to be the neutral element of the union).
Try it with an initializer:
allkey = reduce(lambda x, y: x.union(y.keys()), alldict, set())
An alternative without any lambdas would be:
allkey = reduce(set.union, map(set, map(dict.keys, alldict)))