Why is the order in dictionaries and sets arbitrary?

Note: This answer was written before the implementation of the dict type changed, in Python 3.6. Most of the implementation details in this answer still apply, but the listing order of keys in dictionaries is no longer determined by hash values. The set implementation remains unchanged. The order is not arbitrary, but depends on the … Read more

How can I get dict from sqlite query?

You could use row_factory, as in the example in the docs: import sqlite3 def dict_factory(cursor, row): d = {} for idx, col in enumerate(cursor.description): d[col[0]] = row[idx] return d con = sqlite3.connect(“:memory:”) con.row_factory = dict_factory cur = con.cursor() cur.execute(“select 1 as a”) print cur.fetchone()[“a”] or follow the advice that’s given right after this example in … Read more

multiprocessing: How do I share a dict among multiple processes?

A general answer involves using a Manager object. Adapted from the docs: from multiprocessing import Process, Manager def f(d): d[1] += ‘1’ d[‘2’] += 2 if __name__ == ‘__main__’: manager = Manager() d = manager.dict() d[1] = ‘1’ d[‘2’] = 2 p1 = Process(target=f, args=(d,)) p2 = Process(target=f, args=(d,)) p1.start() p2.start() p1.join() p2.join() print d … Read more

Accessing a Dictionary.Keys Key through a numeric index

As @Falanwe points out in a comment, doing something like this is incorrect: int LastCount = mydict.Keys.ElementAt(mydict.Count -1); You should not depend on the order of keys in a Dictionary. If you need ordering, you should use an OrderedDictionary, as suggested in this answer. The other answers on this page are interesting as well.

initializing a Guava ImmutableMap

Notice that your error message only contains five K, V pairs, 10 arguments total. This is by design; the ImmutableMap class provides six different of() methods, accepting between zero and five key-value pairings. There is not an of(…) overload accepting a varags parameter because K and V can be different types. You want an ImmutableMap.Builder: … Read more

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