array initialized to “None” in Python

I see a piece of python code

/*Constructor*/
self.matrix={}

/*my funciton*/
if(self.matrix.get((packet.src,packet.dst))==None):

does a python array get initialized to None? What does none represent ? Is the above comparision correct?I am a newbie in python and trying to relate to C++ concepts

Answers


self.matrix isn't an array, it is a dict. This is comparable to a std::map in C++. From your usage, it is like a std::map<std::pair<srcType, dstType>, valueType>. (Note that dicts can hold variant types both in the key and the value -- I'm only assuming that it'll always use a tuple of 2 elements as the key.)

And no, self.matrix isn't initialized to None. dict.get() returns None if it can't find a match. As an alternative, [] throws a KeyError exception if it can't find a match.


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