python中的del比较特殊，因为python都是引用，del只是操作变量，而不是数据对象上
官方文档解释

The del statement
del_stmt ::= "del" target_list
Deletion is recursively defined very similar to the way assignment is defined. Rather than spelling it out in full details, here are some hints.
Deletion of a target list recursively deletes each target, from left to right.
Deletion of a name removes the binding of that name from the local or global namespace, depending on whether the name occurs in a global statement in the same code block. If the name is unbound, a NameError exception will be raised.
Deletion of attribute references, subscriptions and slicings is passed to the primary object involved; deletion of a slicing is in general equivalent to assignment of an empty slice of the right type (but even this is determined by the sliced object).
Changed in version 3.2: Previously it was illegal to delete a name from the local namespace if it occurs as a free variable in a nested block

大概意思就是删除目标列表将从左到右递归删除每个目标，删除变量名称将从本地或者全局命名空间中移除该名称的绑定
下面举例说明下
例1

    a=1       # 对象1 被变量a引用，对象1的引用计数器为1  
    b=a       # 对象1 被变量b引用，对象1的引用计数器加1  
    c=a       # 对象1 被变量c引用，对象1的引用计数器加1  
    del a     #删除变量a，解除a对1的引用  
    del b     #删除变量b，解除b对1的引用  
    print(c)  #最终变量c仍然引用1  

例2

li = [1, 2, 3, 4, 5]  # 列表本身不包含数据1,2,3,4,5，而是包含变量：li[0] li[1] li[2] li[3] li[4]
first = li[0]  # 拷贝列表数据，不会有数据对象的复制，而是创建新的变量引用
del li[0] # 删除li[0]对对象1的引用 
print(li[0])  # 输出[2, 3, 4, 5]
print(first)  # 输出 

总结：

del删除的只是变量，没有删除对变量的引用。