CODEWITHSUNDEEP
python-3.x
user2003548
user2003548

Reputation: 4545

how to override dict [] action in python?

i want to store a certain kind of object in a dictionary. the object has an attribute called 'lastAccessDate',whenever the program access the object, i hope the object's attribute update to current system time,which like this 

def getValue(key):
    obj = objectDict.get(key,None)
    if obj is not None:
        obj.lastAccessDate = getSystemDate()
    return obj

the program must throught this api to access the object, otherwise it's would be a bug.i hope i can operate the dict like normal dict,when i use objectDict[key] or objectDict.get() to access the key,it will do this thing automatically.how to implement it in python?

Upvotes: 1

Views: 238

Answers (1)

Yann Ramin
Yann Ramin

Reputation: 33197

You can re-implement or provide the [] accessor via __getitem__ which would appear to make your custom object be a dict. If you need to provide set support, implement __setitem__

http://docs.python.org/2/reference/datamodel.html#emulating-container-types

Upvotes: 1

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