Python 在执行LPTHW的练习47时获取断言错误

我正在做艰苦学习Python的练习47，我得到一个错误提示：

Traceback (most recent call last):
File "c:\python26\lib\site-packages\nose-1.2.0-py2.6.egg\nose
97, in runTest
self.test(*self.arg)
File "E:\project\ex47\tests\ex47_tests.py", line 27, in test_
assert_equal(start.go('down').go('up'),start)
AssertionError: None != <ex47.game.Room object at 0x0191BFD0>

#while executing the below code: 

from nose.tools import *
from ex47.game import Room

def test_room():
    gold=Room("GoldRoom",
                """This room has gold in it you can grab. There's a
                door to the north.""")
    assert_equal(gold.name,"GoldRoom")
    assert_equal(gold.paths,{})

def test_room_paths():
    center = Room("Center","Test room in the center.")
    north = Room("North","Test room in the north.")
    south = Room("South", "Test room in the south.")
    center.add_paths({'north':north,'south': south})
    assert_equal(center.go('north'),north)
    assert_equal(center.go('south'),south)

def test_map():
    start = Room("start", "You can go west and down a hole.")
    west = Room("Trees","There are trees here, you can go east.")
    down = Room("Dungeon","It's dark down here, you can go up.")
    start.add_paths({'west':west,'down':down})
    west.add_paths({'east':start})
    assert_equal(start.go('west'),west)
    assert_equal(start.go('west').go('east'),start)
    assert_equal(start.go('down').go('up'),start)

---

您没有显示正在测试的实际代码，但某处可能缺少一条

返回

语句。

您从未向

下

房间添加过

向上

路径

down = Room("Dungeon","It's dark down here, you can go up.")

所以你的失败就在这条线上

assert_equal(start.go('down').go('up'),start)

start.go（'down'）

返回

down-Room

对象，该对象没有

up

的路径。它从

get（）

调用返回

None

，并再次比较

start

对象。由于

None！=开始

看起来您需要这条线：

down.add_paths({'up', start})

down.add_paths({'up', start})