In [23]: m = {'a' : 1, 'b' : 2}

In [24]: 'a' in m and m['c'] == 3
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-24-3db18402cae3> in <module>()
----> 1 'a' in m and m['c'] == 3

KeyError: 'c'