为什么这段代码不起作用？ （蟒蛇）

Question

class MyClass:

     def __init__(self):
         pass

     val = ""

     def getval(self):
         # code to get val 
         # ... and at the end:
         self.val = "bla bla"

     self.getval()
     print val

现在在这一点上它说没有找到名称self。如果我只尝试getval()（没有自己的前缀），那么它表示没有getval方法接受0个参数。请有人能解释一下为什么这段代码不起作用？

Answer 1

这是一个更有意义的例子：

class MyClass:
     def __init__(self):
         pass

     # this is a class variable
     val = ""

     def getval(self):
         # code to get val 
         # ... and at the end:
         self.val = "bla bla"
         return self.val

# make a instance of the class
x = MyClass()
print x.getval()

# MyClass.val is a different class variable
print MyClass.val

Read the Python tutorial

Answer 2

您尚未创建对象的实例。

class MyClass:
    def __init__(self):
        pass

    val = ""

    def getval(self):
        # code to get val 
        # ... and at the end:
        self.val = "bla bla"

     self.getval()
     print val

o = MyClass()
print o.getval()