如何访问python中嵌套字典键的值？

Question

我有嵌套的字典，我想更新第二个字典键值的值，这样它也应该反映字典值。

class Screen_Seat:
   def __init__(self,screen,show,num_seats,day):
      self.screen_id = screen
      self.show = show
      self.num_seats = num_seats

     self.seats = {('screen1','day4'):{'show1':100,'show2':100,'show3':100,'show4':100},
                   ('screen1','day5'):{'show1':100,'show2':100,'show3':100,'show4':100},
                   ('screen1','day6'):{'show1':100,'show2':100,'show3':100,'show4':100},
                   ('screen1','day7'):{'show1':100,'show2':100,'show3':100,'show4':100},}

我想更新以下键的值

self.seats['screen1','day4','show4'] =90

以便：

self.seats = {('screen1','day4'):{'show1':100,'show2':100,'show3':100,'show4':**90**},
                       ('screen1','day5'):{'show1':100,'show2':100,'show3':100,'show4':100},
                       ('screen1','day6'):{'show1':100,'show2':100,'show3':100,'show4':100},
                       ('screen1','day7'):{'show1':100,'show2':100,'show3':100,'show4':100},}

我怎么能在python中做到这一点？

编辑：

class Screen_Seat:
   def __init__(self,screen,show,num_seats,day):
      self.screen_id = screen
      self.show = show
      self.num_seats = num_seats

      self.seats = {('screen1','day4'):{'show1':100,'show2':100,'show3':100,'show4':100},
      ('screen1','day5'):{'show1':100,'show2':100,'show3':100,'show4':100},
      ('screen1','day6'):{'show1':100,'show2':100,'show3':100,'show4':100},
      ('screen1','day7'):{'show1':100,'show2':100,'show3':100,'show4':100},
          ('screen2','day1'):{'show1':100,'show2':100,'show3':100,'show4':100},
      ('screen2','day2'):{'show1':100,'show2':100,'show3':100,'show4':100},
      ('screen2','day3'):{'show1':100,'show2':100,'show3':100,'show4':100},
                     }

class Screen_Booking(screen_seat):
   def __init__(self,screen,show,num_seats,day):
       screen_seat.__init__(self,screen,show,num_seats,day)
       self.booking_screen = screen
       self.booking_show = show
       self.booking_day=day
       self.booking_seats=num_seats

   def CheckAvailability(self):
       self.seats[self.booking_screen,self.booking_day][self.booking_show]
       if (self.seats[self.booking_screen,self.booking_day][self.booking_show] > int(self.booking_seats)):
          self.seats[self.booking_screen,self.booking_day][self.booking_show]=(self.seats[self.booking_screen,self.booking_day][self.booking_show]-int(self.booking_seats))

          #print self.seats[self.booking_screen,self.booking_day][self.booking_show]
          print 'seat booked'
       else:
           print 'Sorry, No seats available in Screen1. Please try other Screens'


A1 = Screen_Booking('screen1','show1','98','day4')
A1.CheckAvailability()
A1 = Screen_Booking('screen1','show1','10','day4')

输出：

2
seat booked
90
seat booked

第二次它应该打印“抱歉，Screen1 中没有可用座位。 请尝试其他屏幕'

帮我找出代码中的问题？

Answer 1

您的字典有两个嵌套级别，一个用('screenX', 'dayX')元组索引，另一个用showX字符串showX 。 请注意以下事项：

>>> foo.seats['screen1', 'day4']
{'show4': 90, 'show2': 100, 'show1': 100, 'show3': 100}
>>> foo.seats['screen1', 'day4']['show4']
90

第一个表达式为您提供了一个字典，您必须再次对其进行索引才能获得所需的元素。 所以最后的表达是：

foo.seats['screen1', 'day4']['show4']
#         ^                  ^
#         |                  |
#         +-- First level    +-- Second level

Answer 2

用这个：

self.seats[('screen1', 'day4')]['show4'] = 90

输出：

self.seats
{('screen1', 'day4'): {'show1': 100, 'show2': 100, 'show3': 100, 'show4': 90},
 ('screen1', 'day5'): {'show1': 100, 'show2': 100, 'show3': 100, 'show4': 100},
 ('screen1', 'day6'): {'show1': 100, 'show2': 100, 'show3': 100, 'show4': 100},
 ('screen1', 'day7'): {'show1': 100, 'show2': 100, 'show3': 100, 'show4': 100}}

首先访问由('screen1', 'day4')元组显示的 screen1 day4 作为self.seats字典中的键。 然后访问'show4'内的字典通过键'show4' ，并将其值设定为90。

看来你是python的新手。 让我们尝试通过以下 3 个步骤来理解思维过程。

第1步：

('screen1', 'day4')可以访问{'show1': 100, 'show2': 100, 'show3': 100, 'show4': 100}内部字典。

self.seats[('screen1', 'day4')]
{'show1': 100, 'show2': 100, 'show3': 100, 'show4': 100}

第2步：

现在通过上一步获得的字典中的'show4'键访问show4 。

self.seats[('screen1', 'day4')]['show4']
100

第三步：

将获得的 screen1-day4-show4 值更新为 90。

self.seats[('screen1', 'day4')]['show4'] = 90

self.seats[('screen1', 'day4')]['show4']
90

代码解决方案：

检查此方法是否适合您。

class ScreenBooking(object):

    def __init__(self):
        super(ScreenBooking, self).__init__()
        self.seats = {
            ('screen1','day4'):{'show1':100,'show2':100,'show3':100,'show4':100},
            ('screen1','day5'):{'show1':100,'show2':100,'show3':100,'show4':100},
            ('screen1','day6'):{'show1':100,'show2':100,'show3':100,'show4':100},
            ('screen1','day7'):{'show1':100,'show2':100,'show3':100,'show4':100},
            ('screen2','day1'):{'show1':100,'show2':100,'show3':100,'show4':100},
            ('screen2','day2'):{'show1':100,'show2':100,'show3':100,'show4':100},
            ('screen2','day3'):{'show1':100,'show2':100,'show3':100,'show4':100},
        }
        self.shows = ['show1', 'show2', 'show3', 'show4']


    def check_valid_details(self, screen, show, day):
        """
        Check if booking details are valid and return True/False accordingly.
        """
        if (screen, day) not in self.seats or show not in self.shows:
            return  False
        return True

    def book_seats(self, screen, show, no_of_seats, day):
        """
        Book seats after checking valid booking details and the remaining seats.
        """
        valid_details = self.check_valid_details(screen, show, day)
        if not valid_details:
            print 'Invalid booking details!'
            return
        show_total_seats = self.seats[(screen, day)][show]
        if show_total_seats > int(no_of_seats):
            show_remaining_seats = show_total_seats - int(no_of_seats)
            self.seats[(screen, day)][show] = show_remaining_seats #update the seats count
            print '%s seat(s) booked'%(no_of_seats)
        else:
            print 'Sorry, No seats available in %s. Please try other Screens'%(screen)

a1 = ScreenBooking()
a1.book_seats('screen1','show1','98','day4')
a1.book_seats('screen1','show1','10','day4')