测试1
>>> a = [1,2,3] # set a to point to a list [1, 2, 3]>>> b = a # set b to what a is currently pointing at>>> a = [] # now you set a to point to an empty list# Step 1: A --> [1 2 3]# Step 2: A --> [1 2 3] <-- B# Step 3: A --> [ ] [1 2 3] <-- B# at this point a points to a new empty list# whereas b points to the original list of a
测试2
>>> a = [1,2,3] # set a to point to a list [1, 2, 3]>>> b = a # set b to what a is currently pointing at>>> del a # delete the reference from a to the list# Step 1: A --> [1 2 3]# Step 2: A --> [1 2 3] <-- B# Step 3: [1 2 3] <-- B# so a no longer exists because the reference# was destroyed but b is not affected because# b still points to the original list
测试3
>>> a = [1,2,3] # set a to point to a list [1, 2, 3]>>> b = a # set b to what a is currently pointing at>>> del a[:] # delete the contents of the original# Step 1: A --> [1 2 3]# Step 2: A --> [1 2 3] <-- B# Step 2: A --> [ ] <-- B# both a and b are empty because they were pointing # to the same list whose elements were just removed
