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If you want to make an existing set empty, you can use the .clear() metod, especially if you want to avoid creating a new object. If you want to do a comparison, use set() or check if the length is 0. example: #create a new set. a=set([1,2,3,'foo','bar']) #or, using a literal: a={1,2,3,'foo','bar'}
4. A set literal is just a tuple of values in curly braces: x = {2, 3, 5, 7} So, you can create an empty set with empty tuple of values in curly braces: x = {*()} Still, just because you can, doesn't mean you should. Unless it's an obfuscated programming, or a codegolf where every character matters, I'd suggest an explicit x = set() instead.
If you want to return True for an empty set, then I think it would be clearer to do: return c == set() i.e. "c is equal to an empty set". (Or, for the other way around, return c != set()). In my opinion, this is more explicit (though less idiomatic) than relying on Python's interpretation of an empty set as False in a boolean context.
The update method in dictionary is used to update the new dictionary from a previous one, like so, >>> abc = {1: 2} >>> d.update(abc) >>> d. {1: 2} Whereas in sets, it is used to add elements to the set. >>> D.update([1, 2]) >>> D.
From Python 3 documentation (the same holds for python 2.7): Curly braces or the set() function can be used to create sets. Note: to create an empty set you have to use set(), not {}; the latter creates an empty dictionary, a data structure that we discuss in the next section. in python 2.7:
The only reason that comes to mind for using a dict instead of set in this case is if you want to iterate the structure in insertion order. – joseville Commented Aug 7, 2022 at 14:08
I also tried x=set() but when I do print(x) it gives output as set() and not {} How do I initialize and print a set such that if it is empty then it should show {} and not set() Example: If the set has contents, then it gets printed as {1,2,3} but if empty then I want it to show as {} (and not as set()). Does this need to be done ...
If I understand your question correctly, you want to delete items in a dictionary where the value is an empty set. for k,v in dict.items(): if v == set(): del dict[k] That should empty out all key value pairs with value of an empty set. As said in the comments, dict.items() is only safe in Python 2.x.
Try this instead: lst = [None] * 10. The above will create a list of size 10, where each position is initialized to None. After that, you can add elements to it: lst = [None] * 10. for i in range(10): lst[i] = i. Admittedly, that's not the Pythonic way to do things. Better do this:
The syntax {1, 2, 3} for sets was introduced with Python 2.7. Since {} has been used for such a long time it will stay as the way to define an empty dictionary. If Python would have had the new set syntax since the beginning, likely an empty set would be defined with {} and an empty dictionary with {:}. edited Sep 11, 2017 at 4:34.