I'm writing an API for my software so that it is easier to access mongodb.
I have this line:
def update(self, recid):
self.collection.find_and_modify(query={"recid":recid}, update={{ "$set": {"creation_date":str( datetime.now() ) }}} )
Which throws TypeError: Unhashable type: 'dict'
.
This function is simply meant to find the document who's recid matches the argument and update its creation_date field.
Why is this error occuring?
It's simple, you have added extra/redundant curly braces, try this:
self.collection.find_and_modify(query={"recid":recid},
update={"$set": {"creation_date": str(datetime.now())}})
UPD (explanation, assuming you are on python>=2.7):
The error occurs because python thinks you are trying to make a set with {}
notation:
The set classes are implemented using dictionaries. Accordingly, the requirements for set elements are the same as those for dictionary keys; namely, that the element defines both __eq__() and __hash__().
In other words, elements of a set should be hashable: e.g. int
, string
. And you are passing a dict
to it, which is not hashable and cannot be an element of a set.
Also, see this example:
>>> {{}}
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'dict'
Hope that helps.
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