在python 3.x中使用isinstance（sample_list，list）时出错

Question

When I run isinstance(names,list) where names is a list, instead of getting True as the result, I get the following error message:

Traceback (most recent call last):
  File "<pyshell#47>", line 1, in <module>
    isinstance(names,list)
TypeError: isinstance() arg 2 must be a type or tuple of types

I am using IDLE and Python 3.x

Could anybody please point out what the problem is.

Answer 1

Because you probably created a variable named list somewhere above in your code.

list = [1, 2, 3]
...
names = ['Joe', 'Jack', 'Jane']
...
if isinstance(names, list):
   ...

---

TypeError: isinstance() arg 2 must be a class, type, or tuple of classes and types

Never use type names such as set , list , file , dict etc. as a variable name in your code.