1. del 函数删除引用，并非对象 (以下代码是直接运行在Ipython console下)

#spyder: example 1
xx = [1,2,3] #赋值
xx #输出xx
Out[2]: [1, 2, 3]
del xx #删除引用，但未删除对象
xx #输出xx，报错

Traceback (most recent call last):
  File "<ipython-input-4-ce3af7760f12>", line 1, in <module>
    xx
NameError: name 'xx' is not defined

#spyder: example 2
xx = [1,2,3]
yy = xx
xx
Out[7]: [1, 2, 3]
yy
Out[8]: [1, 2, 3]
del xx
xx #输出xx报错

Traceback (most recent call last):
  File "<ipython-input-10-ce3af7760f12>", line 1, in <module>
    xx
NameError: name 'xx' is not defined

yy #输出yy
Out[11]: [1, 2, 3]

# 参考：https://www.cnblogs.com/xisheng/p/7340514.html