Union of all keys from a list of dictionaries

Question

Say I have a list of dictionaries. They mostly have the same keys in each row, but a few don't match and have extra key/value pairs. Is there a fast way to get a set of all the keys in all the rows?

Right now I'm using this loop:

def get_all_keys(dictlist):
    keys = set()
    for row in dictlist:
        keys = keys.union(row.keys())

It just seems terribly inefficient to do this on a list with hundreds of thousands of rows, but I'm not sure how to do it better

Thanks!

Answer 1

You could try:

def all_keys(dictlist):
    return set().union(*dictlist)

Avoids imports, and will make the most of the underlying implementation of set. Will also work with anything iterable.