python 清空列表

方法：直接賦值為空list

對於一個一維list：

>>> a = [1,2,3]
>>> a = []
>>> a
[]

對於一個二維list：

>>> a = [[1,2,3,4,5],[6,7,8,9,10]]
>>> a = [[],[]]
>>> a
[[], []]

想清空二維list中的某一維;

>>> a = [[1,2,3,4,5],[6,7,8,9,10]]
>>> a[0] = []
>>> a
[[], [6, 7, 8, 9, 10]]