在Python中使用装饰器进行类型检查

Question

这更像是一个语法错误问题,我正在尝试在Python修饰器上做这个教程

http://www.learnpython.org/page/Decorators

我的尝试代码

def Type_Check(correct_type):
    def new_function(old_function):
        def another_newfunction(arg):
            if(isintance(arg, correct_type)):
                return old_function(arg)
            else:
                print "Bad Type"

    #put code here

@Type_Check(int)
def Times2(num):
    return num*2

print Times2(2)
Times2('Not A Number')

@Type_Check(str)
def First_Letter(word):
    return word[0]

print First_Letter('Hello World')
First_Letter(['Not', 'A', 'String'])

我想知道什么是错的,请帮忙

Answer 1

看起来你忘了在装饰器的末尾返回新定义的函数:

def Type_Check(correct_type):
    def new_function(old_function):
        def another_newfunction(arg):
            if(isinstance(arg, correct_type)):
                return old_function(arg)
            else:
                print "Bad Type"
        return another_newfunction
    return new_function

编辑:还有一些类型,由andrean修复