isinstance（object，type）给我一个错误-另外，展平嵌套列表

Question

I am a beginner programmer, and I attempted to solve one of the prolog questions which was to flatten a nested list. My attempt:

a = [1, 2, 3, [1, 2, 3], 4, 5]

def flatten(list):
    new = []
    for i in list:
        new.append(','.join(int(i)) for i in list)
    for ele in list:
        if isinstance(ele, list):
            flatten(ele)
            return new
        else:
            pass
        return new

flatten(a)

I get an error saying:

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

I thought I implemented it correctly since I passed on ele (the object) and list (type)? It worked in the interpreter, but not here.

Also any advice for the code in terms of trying to flatten a nested list?

Answer 1

By doing def flatten(list) , you used list as the name of your function parameter, which blocks access to the builtin type named list . Use a different name for your variable.

As for how to flatten nested lists, googling that question will give you dozens if not hundreds of answers.

Answer 2

You are defining list as variable in your flatten(list) function.

Please avoid to use variable name of data type. Please change it to flatten(my_list) it will work.

Answer 3

there are some flaw in your code:

1 never use list as variable name
2 new.append(','.join(int(i)) for i in list)  
   `join` wont take int type, will raise TypeError
    it should be new.append(','.join(str(i)))
3 you are using `return` once it returned , it come out of the function