Python开发[类型错误]

Question

我是一个初学者，最近开始了python开发。 我正在研究的代码：

import random 
import textwrap

def show_message(dotted_line,width):

    print(dotted_line)
    print("\033[1m"+ "Attack of clones:" + "\033[0m")

    message = (
    "The war between humans and their arch enemies , Clones was in the offing. Obi-Wan, one of the brave Jedi on his way ," 
    "he spotted a small isolted settlement .Tired and hoping to replenish his food stock , he decided to take a detour." 
    "As he approached the village, he saw five residence , there was no one to be seen around.He decided to enter" )
    print(textwrap.fill(message, width = width))

def show_mission(dotted_line):
    print("\033[1m"+ "Mission:" + "\033[0m")
    print('\t Choose the hit where Obi wan can rest...')
    print("\033[1m"+ "TIP:" + "\033[0m")
    print("Be careful as there are Stormtroopers lurking around!")
    print(dotted_line)


def occupy_huts():
    global huts
    huts = []

    while len(huts) < 5:
        random_choice = random.choice(occupants)
        huts.append(random_choice)



def process_user_choice(): 
     message = "\033[1m"+ "Choose the hut to enter (1-5) " + "\033[0m"
     uc = input("\n" + message)
     index = int(uc)
     print("Revealing the occupants...")
     message = ""



def reveal_occcupants(index,huts,dotted_line):
    for i in range (len(huts)):
        occupant_info = "<%d:%s>"%(i+1,huts[i])
        if i + 1 == index:

            occipant_info = "\033[1m"+ "" + "\033[0m"
        message += occupant_info + " "
    print("\t" + message)
    print(dotted_line)



def enter_huts(index,huts,dotted_line): 
    print("\033[1m"+ "Entering Hut %d ..." %index + "\033[0m")

    if huts[index - 1] == 'clones':
        print("\033[1m"+ "There's Stormtrooper Here!!" + "\033[0m")
    else:
        print("\033[1m"+ "It's Safe here!" + "\033[0m")
    print(dotted_line)



def run():
    keep_playing = 'y'
    global occupants
    occupants = ['clones','friend','Jedi Hideout']
    width = 70
    dotted_line = '-' * width

    show_message(dotted_line, width)
    show_mission(dotted_line)

    while keep_playing == 'y':
         huts = occupy_huts()
         index = process_user_choice()
         reveal_occcupants(index,huts,dotted_line)
         enter_huts(index,huts,dotted_line)
         keep_playing = raw_input("Play Again?(y/n)")

if __name__ == '__main__':
    run()

错误就在 def显示乘员。 “类型错误：类型为'NoneType'的对象没有len（）”

如何克服这个错误，请提出一个替代方法

Answer 1

len（）方法接受对象作为参数。 在您的例子中，在第43行，huts可能没有，因此您可能会得到一个错误。你知道吗

您应该在第42行后插入如下条件

if huts is None:
    return

Answer 2

我的猜测是“huts”不是类型，因为从来没有调用过occupt_huts（）。或者“huts”变量的作用域有问题——这可以通过将其声明为函数的一个空集来解决。你知道吗

此外，还可以利用Python的语法，将第43行更改为“for hut in huts:”。如果您还需要小屋的索引，请尝试“for hut，i-hut in enumerate（huts）：”。你知道吗

Answer 3

此处：

while keep_playing == 'y':
     huts = occupy_huts()

您的occupy_huts()函数不返回任何内容（它填充了一个全局变量huts，但不返回它），因此huts = occupy_huts()语句huts后面的现在是None（如果您不显式返回某些内容，则为默认函数返回值）。然后将这个（现在是None）huts变量传递给reveal_occupants()：

    reveal_occcupants(index,huts,dotted_line)

解决方案很简单：修改occupy_huts，因此它不处理全局变量（这几乎总是一个非常糟糕的主意）并返回None，而是处理局部变量并返回它：

def occupy_huts():
    huts = []
    while len(huts) < 5:
        random_choice = random.choice(occupants)
        huts.append(random_choice)
    return huts

当我们使用它时，您也在使用global来表示occupants，这是脆弱的（occupy_huts()如果在创建此变量之前调用，则会中断），而您可以将其作为参数传递：

def occupy_huts(occupants):
    huts = []
    while len(huts) < 5:
        random_choice = random.choice(occupants)
        huts.append(random_choice)
    return huts

然后在run()：

def run():
    keep_playing = 'y'
    occupants = ['clones','friend','Jedi Hideout']
    # ...
    while keep_playing == 'y':
         huts = occupy_huts(occupants)

有趣的是，你传递的参数通常是常量，对程序的逻辑没有影响（即dotted_lines），但是对重要的事情使用全局变量-实际上应该是相反的方式（在你的模块开始时声明虚线为伪常量，不用麻烦把它传递给函数）；)你知道吗

另外，请注意，这里的process_user_choice()也有类似的问题：

while keep_playing == 'y':
     huts = occupy_huts()
     index = process_user_choice()

因为process_user_choice()函数也不返回任何内容。您应该修改它，使它返回其局部变量index。你知道吗