In this document, the variables xs and ys will reappear. They start with these states and mutate as the document goes along:
xs = list(range(10)) # Reminder: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
ys = list(range(10))For a mutable, slicable collection xs, xs.append(x) is intended to be identical to xs[len(xs):] = [x].
xs.append(10)
ys[len(ys):] = [10]After these operations, xs and ys are still equal.
To add a variable number of elements to the end of an array, use extend. xs.extend(ys) is equal in effect to xs[len(xs):] = ys.
xs.extend(range(11, 21))
ys[len(ys):] = range(11, 21)After these operations, xs and ys are still equal.
To remove elements, use remove.
xs.remove(20)
del ys[ys.index(20)]pop can be used to remove and return a value from the list. It takes an optional index as an argument, which, if unprovided, causes the
last element to be removed.
print(xs.pop()) # 19