It’s part of an evolution. Originally, Python items() built a real list of tuples and returned that. That could potentially take a lot of extra memory. Then, generators were introduced to the language in general, and that method was reimplemented as an iterator-generator method named iteritems(). The original remains for backwards compatibility. One of Python … Read more
Like this: keys = [‘a’, ‘b’, ‘c’] values = [1, 2, 3] dictionary = dict(zip(keys, values)) print(dictionary) # {‘a’: 1, ‘b’: 2, ‘c’: 3} Voila 🙂 The pairwise dict constructor and zip function are awesomely useful.
Personally, I would use the map, as its use implies a data lookup – using a switch usually indicates a difference in program behavior. Furthermore modifying the data mapping is easier with a map than with a switch. If performance is a real issue, profiling is the only way to get a usable answer. A … Read more
Like the error message suggests, dictionaries in Python do not provide an append operation. You can instead just assign new values to their respective keys in a dictionary. mydict = {} mydict[‘item’] = input_value If you’re wanting to append values as they’re entered you could instead use a list. mylist = [] mylist.append(input_value) Your line … Read more
As you note, you can store the items to delete somewhere and defer the deletion of them until later. The problem then becomes when to purge them and how to make sure that the purge method eventually gets called. The answer to this is a context manager which is also a subclass of dict. class … Read more
This is simply how the get() method is defined. From the Python docs: Return the value for key if key is in the dictionary, else default. If default is not given, it defaults to None, so that this method never raises a KeyError. The default “not-found” return value is None. You can return any other … Read more
For an OrderedDict it’s inherently O(n) because the ordering is recorded in a linked list. For the builtin dict, there’s a vector (a contiguous array) rather than a linked list, but pretty much the same thing in the end: the vector contains a few kind of “dummies”, special internal values that mean “no key has … Read more
In response to questions about performance in relation to the number of missed searches, I have refactored the test to parameterise this. Example results: searches set_size miss ordered unordered flat_map 1000000 0 100% 4384 12901 681 1000000 99 99.99% 89127 42615 86091 1000000 172 99.98% 101283 53468 96008 1000000 303 99.97% 112747 53211 107343 1000000 … Read more
You are missing the const in the first type of the pair. [](std::pair<const std::string, std::string>& p) { However this is not your problem: You cannot use a map as the OutputIterator, as they do not support assignment. You can, however mutate the second argument using std::for_each. Good old map_to_foobar: std::for_each(data.begin(), data.end(), [](std::pair<const std::string, std::string>& p) … Read more
You can write a single element tuple as @larsmans explained, but it is easy to forget the trailing comma. It may be less error prone if you just use lists as the parameters to the set constructor and methods: Dictionary[key_1] = set([‘name’]) Dictionary[key_2] = set([‘name_2’, ‘name_3’]) Dictionary[key_2].add([‘name_3’]) should all work the way you expect.