python list中方法的时间复杂度_list.pop(0)的时间复杂度

pop(0) is slower than pop():
When pop is called on the end of the list it takes O(1) but when pop is called on the first element in the list or anywhere in the middle it is O(n). The reason for this lies in how Python chooses to implement lists. When an item is taken from the front of the list, in Python’s implementation, all the other elements in the list are shifted one position closer to the beginning. This may seem silly to you now, but if you look at Table 2 you will see that this implementation also allows the index operation to be O(1). This is a tradeoff that the Python implementors thought was a good one.