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I think this post explains it well: Dictionary Merge and Update Operators in Python 3.9: Here a summary: The Dictionary Update Operator. Dictionary x is being updated by the dictionary y. x.update(y) print(x) The Dictionary Merge Operator: Fuse them into a new one. Having:
2. Make sure you have same type of the key you are trying to update. If it was a string in the dict, then when updating, use a string. If you do otherwise, python will see it as a different key and add one. answers = {1: None, 2: None, 3: None} answers[1] = 'some text'.
2. I made a simple function, in which you give the key, the new value and the dictionary as input, and it recursively updates it with the value: def update(key,value,dictionary): if key in dictionary.keys(): dictionary[key] = value. return. dic_aux = [] for val_aux in dictionary.values(): if isinstance(val_aux,dict):
For “an expression that expects a value to exist”, but you don't want to update the dict, you would simply use get with a default value. The whole point of setdefault is that it does perform the update – which then also naturally provides an lvalue for the element in question, but whether or not you immediately use that is up to you.
68. If you want to add a dictionary within a dictionary you can do it this way. Example: Add a new entry to your dictionary & sub dictionary. dictionary = {} dictionary["new key"] = "some new entry" # add new dictionary entry. dictionary["dictionary_within_a_dictionary"] = {} # this is required by python.
Unsubstantiated rhetoric like "Deep copy is considered harmful" is unhelpful. All else being equal, shallow copying a complex data structure is significantly more likely to yield unexpected edge case issues than deep copying the same structure.
z = x.copy() z.update(y) return z. and then you have a single expression: z = merge_two_dicts(x, y) You can also make a function to merge an arbitrary number of dictionaries, from zero to a very large number: def merge_dicts(*dict_args): """. Given any number of dictionaries, shallow copy and merge into a new dict,
If keyword arguments are specified, the dictionary is then updated with those key/value pairs: d.update(red=1, blue=2). map() is a built-in method that produces a sequence by applying the elements of the second (and subsequent) arguments to the first argument, which must be a callable. Unless your key object is a callable and the value object ...
Functions compute new values out of their parameters (including any target object); procedures modify objects and don't return anything (i.e. they return None). So procedures have side effects, functions don't. update is a procedure, hence it doesn't return a value.
What you could do, instead of calling .update() on the existing dict, is add a sub-dict. Its key could be the name of the source from which you gathered the information. The value could be the dict you receive from the source, and if you need to store more than 1 dict of the same source you can store them in a list. Example.