>>> def fun1(d):
...     print d['key1']
...     print d['key2']
...     
... 
>>> D={'KEY1': 1, 'KEY2': 2}
>>> fun1(D)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "<input>", line 2, in fun1
KeyError: 'key1'
>>> D2={'key1': 1, 'key2': 2}
>>> fun1(D2)
1
2
>>>