how to use .get() in a nested dict?

Question

I use .get() to query for keys which may or may not be present in a dictionary.

In [1]: a = {'hello': True}
In [3]: print(a.get('world'))
None

I have, however, dictionaries where the key I want to check for is deeper in the structure and I do not know if the ancestors are present or not. If the dict is b = {'x': {'y': {'z': True}}} do I have to resort to

In [5]: b.get('x') and b['x'].get('y') and b['x']['y'].get('z')
Out[5]: True

to check for 'z' when I do not know whether 'x' and 'y' exist?

Answer 1

You can return an empty dictionary object from dict.get() to ease chaining calls:

b.get('x', {}).get('y', {}).get('z')

but perhaps you'd be better off catching the KeyError exception:

try:
    value = b['x']['y']['z']
except KeyError:
    value = None