In [5]: from types import MappingProxyType
In [6]: d = {1:'a'}
In [7]: d_proxy = MappingProxyType(d)
In [8]: d_proxy[1]
Out[8]: 'a'
In [9]: d_proxy
Out[9]: mappingproxy({1: 'a'})
In [10]: d_proxy[2]
------------------------------------------------------------
KeyError Traceback (most recent call last)
<ipython-input-10-6f9dce4cd735> in <module>
----> 1 d_proxy[2]
KeyError: 2
In [11]: d_proxy[2] = 'x'
------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-11-bc17a9a62754> in <module>
----> 1 d_proxy[2] = 'x'
TypeError: 'mappingproxy' object does not support item assignment
In [12]: d[2] = 'x'
In [13]: d_proxy
Out[13]: mappingproxy({1: 'a', 2: 'x'})
