I have a piece of code here that is supposed to return the least common element in a list of elements, ordered by commonality: def getSingle(arr): from collections import Counter c = Counte...
The first, [:], is creating a slice (normally often used for getting just part of a list), which happens to contain the entire list, and thus is effectively a copy of the list. The second, list(), is using the actual list type constructor to create a new list which has contents equal to the first list.
The first way works for a list or a string; the second way only works for a list, because slice assignment isn't allowed for strings. Other than that I think the only difference is speed: it looks like it's a little faster the first way. Try it yourself with timeit.timeit () or preferably timeit.repeat ().
If your list of lists comes from a nested list comprehension, the problem can be solved more simply/directly by fixing the comprehension; please see How can I get a flat result from a list comprehension instead of a nested list?. The most popular solutions here generally only flatten one "level" of the nested list. See Flatten an irregular (arbitrarily nested) list of lists for solutions that ...
@Sandy Chapman: List.of does return some ImmutableList type, its actual name is just a non-public implementation detail. If it was public and someone cast it to List again, where was the difference? Where is the difference to Arrays.asList, which returns a non-public List implementation, that throws an exception when attempting add or remove, or the list returned by Collections ...
A List uses an internal array to handle its data, and automatically resizes the array when adding more elements to the List than its current capacity, which makes it more easy to use than an array, where you need to know the capacity beforehand.
List is an Interface, you cannot instantiate an Interface, because interface is a convention, what methods should have your classes. In order to instantiate, you need some realizations (implementations) of that interface.
Don't use quotes on the command line 1 Don't use type=list, as it will return a list of lists This happens because under the hood argparse uses the value of type to coerce each individual given argument you your chosen type, not the aggregate of all arguments. You can use type=int (or whatever) to get a list of ints (or whatever)
The notation List<?> means "a list of something (but I'm not saying what)". Since the code in test works for any kind of object in the list, this works as a formal method parameter. Using a type parameter (like in your point 3), requires that the type parameter be declared. The Java syntax for that is to put <T> in front of the function. This is exactly analogous to declaring formal parameter ...
