Use frozenset, To represent a set of sets, the inner sets must be frozenset objects for the reason that the elements of a set must be hashable (all of Python’s immutable built-in objects are hashable). frozenset is immutable and set is mutable.
IEnumerable describes behavior, while List is an implementation of that behavior. When you use IEnumerable, you give the compiler a chance to defer work until later, possibly optimizing along the way. If you use ToList() you force the compiler to reify the results right away. Whenever I’m “stacking” LINQ expressions, I use IEnumerable, because by … Read more
Well you certainly can use a List<List<string>> where you’d then write: But why would you do that instead of building your own class to represent a track, with Track ID, Name, Artist, Album, Play Count and Skip Count properties? Then just have a List<Track>.
Python 2.7 and 3.2 added the collections.Counter class, which is a dictionary subclass that maps elements to the number of occurrences of the element. This can be used as a multiset. You can do something like this: As well, if you want to check that every element in b is in a: But since you … Read more
When you assign a variable (x = …), you are creating a variable in the current scope (e.g. local to the current function). If it happens to shadow a variable fron an outer (e.g. global) scope, well too bad – Python doesn’t care (and that’s a good thing). So you can’t do this: and expect 1. … Read more
The tuple function takes only one argument which has to be an iterable tuple([iterable]) Return a tuple whose items are the same and in the same order as iterable‘s items. Try making 3,4 an iterable by either using [3,4] (a list) or (3,4) (a tuple) For example will work
Almost always List is preferred over ArrayList because, for instance, List can be translated into a LinkedList without affecting the rest of the codebase. If one used ArrayList instead of List, it’s hard to change the ArrayList implementation into a LinkedList one because ArrayList specific methods have been used in the codebase that would also require restructuring. You can read about the List implementations here. You may start with an ArrayList, but soon after discover that … Read more
or: The default sort mode is ascending. To sort in descending order use the option reverse=True: or:
This is how I did it and it works: It gives you a list of n empty dictionaries.
Try list(newdict.keys()). This will convert the dict_keys object to a list. On the other hand, you should ask yourself whether or not it matters. The Pythonic way to code is to assume duck typing (if it looks like a duck and it quacks like a duck, it’s a duck). The dict_keys object will act like a list for most purposes. … Read more