Speedups In Looping Structures

I notice some interesting behavior when it comes to building lists in different ways. .append takes longer than list-comprehensions, which take longer than map, as shown in the exp

Solution 1:

First, in python3.x, map returns an iterable, NOT a list, so that explains the 50kx speedup there. To make it a fair timing, in python3.x you'd need list(map(...)).

Second, .append will be slower because each time through the loop, the interpretter needs to look up the list, then it needs to look up the append function on the list. This additional .append lookup does not need to happen with the list-comp or map.

Finally, with the list-comprehension, I believe the function square needs to be looked up at every turn of your loop. With map, it is only looked up when you call map which is why if you're calling a function in your list-comprehension, map will typically be faster. Note that a list-comprehension usually beats out map with a lambda function though.