对使用Python中的两个函数修改列表感到困惑

Question

我目前正在阅读埃里克·马特思的Python速成班，我很难理解第8章，第8章都是关于函数的。我被困在练习8-10中，它要求我使用一个新的函数来更改上一次练习中使用的列表。

下面是练习：

8-9. Magicians: Make a list of magician's names. Pass the list to a function called show_magicians(), which prints the name of each magician in the list.

8-10. Great Magicians: Start with a copy of your program from exercise 8-9. Write a function make_great() that modifies the list of magicians by adding the phrase the great to each magician's name. Call show_magicians() to see that the list has actually been modified.

这里是我8-9:的代码

def show_magicians(names):
    """Print each magician name"""
    for name in names:
        msg = name.title()
        print(msg)

magician_names = ['sonic', 'tails', 'knuckles']
show_magicians(magician_names)

我在这个网站上看到了一个非常相似的话题，所以我尝试使用这个页面第一个答案中的代码来帮助我：Python crash course 8-10

然而，我的代码似乎仍然是不正确的，因为编译器在每个名称之后打印3次“伟大”。

这里是我为8-10使用的当前代码

def show_magicians(names):
    """Print each magician name"""
    for name in names:
        msg = name.title()
        print(msg)

magician_names = ['sonic', 'tails', 'knuckles']
show_magicians(magician_names)

def make_great(list_magicians):
    """Add 'Great' to each name."""
    for magician_name in magician_names:
        for i in range(len(list_magicians)):
            list_magicians[i] += " the great!"

make_great(magician_names)
show_magicians(magician_names)

我不知道为什么，但似乎我一直在努力完成这一章的功能。有没有人会有推荐的教程来帮助我更好地理解函数？谢谢您抽时间见我。

Answer 1

好的，你在外面有一个额外的循环，去掉它。最后代码：

def show_magicians(names):
    """Print each magician name"""
    for name in names:
        msg = name.title()
        print(msg)

magician_names = ['sonic', 'tails', 'knuckles']
show_magicians(magician_names)

def make_great(list_magicians):
    """Add 'Great' to each name."""
    for index, item in enumerate(list_magicians):
        list_magicians[index] += " the great!"

make_great(magician_names)
show_magicians(magician_names)

你在做for-in和for-in range。这使得代码重复了字符串的追加。让我解释一下你之前的计划：

解释:在每次迭代中，都会使用for-in循环，使其循环内环3次。因此，外部循环每迭代一次，它会重复内部循环3次，使其在每个名称中追加3次the great。

此外，作为链接问题的答案，我宁愿您使用enumerate而不是range(len(list_magicians))。

Answer 2

将第二种方法更改为：

def make_great(list_magicians):
    """Add 'Great' to each name."""
    i = 0
    for magician_name in magician_names:
        list_magicians[i] += " the great!"
        i += 1

目前，您正在使用两个for loops循环两次，导致添加了3次！

Answer 3

让我们看看您的make_great函数：

def make_great(list_magicians):
    """Add 'Great' to each name."""
    for magician_name in magician_names:
        for i in range(len(list_magicians)):
            list_magicians[i] += " the great!"

这是干什么用的？

for magician_name in magician_names:通过magician_names循环。

for i in range(len(list_magicians)):按索引遍历list_magicians。

list_magicians[i] += " the great!"将the great!添加到list_magicians的ith元素中。

没有必要使用哪一行代码？

for magician_name in magician_names:循环通过这是没有用的。因为它的长度是3，所以在每个元素中添加了3个the great!。删除这一行代码，函数就会正常工作。