With new_list = my_list, you don’t actually have two lists. The assignment just copies the reference to the list, not the actual list, so both new_list and my_list refer to the same list after the assignment. To actually copy the list, you have various possibilities: You can use the builtin list.copy() method (available since Python 3.3):new_list = old_list.copy() You can slice it:new_list … Read more
list() converts the iterable passed to it to a list. If the itertable is already a list then a shallow copy is returned, i.e only the outermost container is new rest of the objects are still the same.
Using an additional state variable, such as an index variable (which you would normally use in languages such as C or PHP), is considered non-pythonic. The better option is to use the built-in function enumerate(), available in both Python 2 and 3:
This is a classic mistake. i in your case is already an element from array (i.e. another list), not an index of array (not an int), so You can check the Python tutorial. Also, try doing this: And see what you get! Also I would advise to stick to naming conventions: variables are normally lower-case (volume, not Volume). In this case i is misleading. row or elem would be much more suitable.
The common approach to get a unique collection of items is to use a set. Sets are unordered collections of distinct objects. To create a set from any iterable, you can simply pass it to the built-in set() function. If you later need a real list again, you can similarly pass the set to the list() function. The following example should cover whatever you … Read more
Either: or: Note that this works only for arrays of reference types. For arrays of primitive types, use the traditional way: Update: It is recommended now to use list.toArray(new Foo[0]);, not list.toArray(new Foo[list.size()]);. From JetBrains Intellij Idea inspection: There are two styles to convert a collection to an array: either using a pre-sized array (like … Read more
Given a list of lists t, which means: is faster than the shortcuts posted so far. (t is the list to flatten.) Here is the corresponding function: As evidence, you can use the timeit module in the standard library: Explanation: the shortcuts based on + (including the implied use in sum) are, of necessity, O(T**2) when there are T sublists — as the intermediate … Read more
Using an additional state variable, such as an index variable (which you would normally use in languages such as C or PHP), is considered non-pythonic. The better option is to use the built-in function enumerate(), available in both Python 2 and 3:
Reference: Data Structures > More on Lists Caveats follow Note that while this is perhaps the cleanest way to answer the question as asked, index is a rather weak component of the list API, and I can’t remember the last time I used it in anger. It’s been pointed out to me in the comments that because this answer is heavily … Read more
First, let’s see what this does:Arrays.asList(ia) It takes an array ia and creates a wrapper that implements List<Integer>, which makes the original array available as a list. Nothing is copied and all, only a single wrapper object is created. Operations on the list wrapper are propagated to the original array. This means that if you shuffle the list … Read more