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I'm analyzing some Python code and I don't know what
pop = population[:] means. Is it something like array lists in Java or like a bi-dimensional array?
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If based on numpy , ans[i,:] means to pick the ith 'row' of ans with all of its 'columns'. Note,when dealing with numpy arrays, we should (almost) always use [i, j] instead of [i][j] . This might be counter-intuitive if you used Python or Java to manipulate matrix before. Follow this answer to receive notifications.
In Python, [::-1] means reversing a string, list, or any iterable with an ordering. For example: hello = "Hello world" nums = [1, 2, 3, 4] print(hello[::-1])
Definition and Usage. The list() function creates a list object. A list object is a collection which is ordered and changeable. Read more about list in the chapter: Python Lists.
arr[:]=arr2 performs an inplace replacement; changing the values of arr to the values of arr2 . The values of arr2 will be broadcasted and copied as needed. arr=arr2 sets the object that the arr variable is pointing to. Now arr and arr2 point to the same thing (whether array, list or anything else).
It is an example of slice notation, and what it does depends on the type of population. If population is a list, this line will create a shallow copy of the list. For an object of type tuple or a str, it will do nothing (the line will do the same without [:]), and for a (say) NumPy array, it will create a new view to the same data.
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