问题
Let's say I have these assignments:
points = []
point = (1, 2)
How come when I do this:
points += point
It works completely fine, and gives me points = [1, 2]. However, If I do something like:
points = points + point
It gives me a TypeError: can only concatenate list (not "tuple") to list. Aren't these statements the same thing, though?
回答1:
The difference, is that list += is equivalent to list.extend(), which takes any iterable and extends the list, it works as a tuple is an iterable. (And extends the list in-place).
On the other hand, the second assigns a new list to points, and attempts to concatenate a list to a tuple, which isn't done as it's unclear what the expected results is (list or tuple?).
来源：https://stackoverflow.com/questions/13332987/list-tuple-vs-list-list-tuple