擅长:python、mysql、java
<pre><code>>>> from itertools import chain
>>> l = [{'x': 42}, {'x': 23, 'y': 5}]
>>> all_keys = set(chain.from_iterable(l))
>>> for d in l:
d.update((k,None) for k in all_keys-d.viewkeys())
>>> l
[{'y': None, 'x': 42}, {'y': 5, 'x': 23}]
</code></pre>