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【已解决】Python 3中判断变量类型

Python crifan 67浏览 0评论

打算是用:

xxx is str

xxx is dict

去判断的:

<code>    def showVideoCallback(self, response):
        print("showVideoCallback: response.url=%s" % (response.url))
        curShowInfoDictOrActId = response.save
        print("curShowInfoDictOrActId=%s" % curShowInfoDictOrActId)

        act_id = ""
        curShowInfoDict = None
        if curShowInfoDictOrActId is str:
            act_id = curShowInfoDictOrActId
            print("para is curActId")
        elif curShowInfoDictOrActId is dict:
            curShowInfoDict = curShowInfoDictOrActId
            print("para is curShowInfoDict")
        else:
            print("!!! can not recognize parameter for showVideoCallback")

</code>

结果无法识别。

然后去搜:

python 3 check variable type

Python: Checking Type of Variable – Code Yarns 👨‍💻

isinstance(s, str)

isinstance(d, dict)

How to check type of object in Python? – Stack Overflow

isinstance(v, type_name)

type(v) is type_name

type(v) == type_name

What is the Pythonic way to check if type of a variable is string? – Quora

How to Use Static Type Checking in Python 3.6 – Adam Geitgey – Medium

How to determine a Python variable’s type? – Stack Overflow

type(i) is int

那isinstance和type有何区别?

python isinstance vs type

python – What are the differences between type() and isinstance()? – Stack Overflow

python – isinstance(foo,bar) vs type(foo) is bar – Stack Overflow

type() vs. isinstance() in Python – Stereochrome

Python中为什么推荐使用isinstance来进行类型判断?而不是type – 简书

【总结】

isinstance:判断某个变量是否是某个类型(或类)的示例

type:只是类型判断,如果是父类集成,则不相等

举例:

<code>class Vehicle:
    pass

class Truck(Vehicle):
    pass
isinstance(Vehicle(), Vehicle)  # returns True
type(Vehicle()) == Vehicle      # returns True
isinstance(Truck(), Vehicle)    # returns True
type(Truck()) == Vehicle        # returns False, and this probably won't be what you want.
</code>

以及:

有些情况下判断结果是错的,不是希望的结果:

<code>class A():
    pass

class B():
    pass

a = A()
b = B()

print(type(a) is type(b))
# True
</code>

暂时就不去研究更加深入的区别了。

结论:

当想要判断变量类型是,优先使用isinstance

此处自己用的是:

<code>        act_id = ""
        curShowInfoDict = None
        if  isinstance(curShowInfoDictOrActId, str):
            act_id = curShowInfoDictOrActId
            print("para is curActId")
        elif isinstance(curShowInfoDictOrActId, dict):
            curShowInfoDict = curShowInfoDictOrActId
            print("para is curShowInfoDict")
        else:
            print("!!! can not recognize parameter for showVideoCallback")
</code>

另外别人举例说明,isinstance支持多个可选的判断:

<code>&gt;&gt;&gt; isinstance(2, float)
False
&gt;&gt;&gt; isinstance('a', (str, unicode))
True
&gt;&gt;&gt; isinstance((2, 3), (str, list, tuple))
True
</code>

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