Question

如何在today功能中使用returntime和return_fee？

import datetime

class Movie(object):
 def __init__(self,title):
    self.title = title

 def time_of_return(self):
    self.today = today
    self.returntime = returntime

    today = datetime.datetime.now()

    returntime = today + datetime.timedelta(days=30)

 def return_fee(Movie):
    fee = -2
    delta = today - returntime

Answer 1

如果您希望time_of_return和return_fee成为实例属性，请从time_of_return拨打__init__进行设置，然后使用self作为前缀：

class Movie(object):
    def __init__(self,title):
        self.title = title
        self.time_of_return()

    def time_of_return(self):
        self.today = datetime.datetime.now()
        self.returntime = today + datetime.timedelta(days=30)

     def return_fee(Movie):
         fee = None
         delta = self.today - self.returntime
         # ... presumably do something else

或者（因为，特别是，today可能会随时间而变化），请从time_of_return内调用函数return_fee，并确保它返回一些内容：

class Movie(object):
    def __init__(self,title):
        self.title = title

    def time_of_return(self):
        today = datetime.datetime.now()
        returntime = today + datetime.timedelta(days=30)
        return today, returntime

     def return_fee(Movie):
         fee = None
         today, returntime = self.time_of_return()
         delta = today - returntime
         # ... presumably do something else

顺便说一句，将代码缩进4个空格是一个好主意。 None（或0）对fee来说是更好的默认值。

Answer 2

我会这样做：

class Movie(object):
 def __init__(self,title):
    self.title = title

 def get_times(self):
    now = datetime.datetime.now()
    return now, now + datetime.timedelta(days=30)

 def time_of_return(self):
    now, returntime = self.get_times()
    return returntime

 def return_fee(self):
    fee = -2
    now, returntime = self.get_times()
    delta = now - returntime
    return <whatever based on fee and delta>

Answer 3

class Movie(object):
 def __init__(self,title,today,returntime):#<----
    self.title = title

 def time_of_return(self):
    self.today = today
    self.returntime = returntime

    today = datetime.datetime.now()

    returntime = today + datetime.timedelta(days=30)

 def return_fee(Movie):
    fee = -2
    delta = today - returntime

那是因为__init__()正在从外部使用for class的参数。但是，当你使用Movie类时，你必须定义那些参数。

Python，如何使用函数外的部分函数

3 个答案: