Question

这是我写的代码：

def show_magicians(magicians):
     """prints the names of magicians"""
    for magician in magicians:
        print(magician)

def make_great(magicians):
    """adds the word great to the string"""
    for magician in magicians:
        magician = magician + " the great"

list_of_magicians = ["Omen", "Carla", "David"]

greats = make_great(list_of_magicians)

print(greats)

从终端运行时我从程序中得到的结果是＆＃34;无＆＃34;。请告诉我代码的问题。

而不是使用print(greats)，使用show_magicians(greats)会给我以下错误：

Traceback (most recent call last):
  File "C:\Users\-myname-\Documents\python_workspace\functions6.py", line 18,    
  in <module>
    show_magicians(greats)
  File "C:\Users\-myname-\Documents\python_workspace\functions6.py", line 5,
  in show_magicians
     for magician in magicians:
 TypeError: 'NoneType' object is not iterable

请给我建议并彻底解释您为修复代码所做的工作。

Answer 1

问题是双重的：

magician = magician + " the great"

会将名称魔术师分配给循环体内的新字符串，但不会对字符串执行任何操作。您没有修改正在迭代的列表。

第二个问题是make_great没有返回任何内容，因此默认返回None。

以下是修复：

def make_great(magicians):
    return [m + " the great" for m in magicians]

这使用列表理解，另一种写入方式是

def make_great(magicians):
    result = []
    for m in magicians:
        result.append(m + " the great")
    return result

请注意，我们实际上正在使用我们创建的新字符串执行某些操作，并且在两种情况下都会返回结果。

Answer 2

两个问题：

您只是更改字符串的副本（for循环创建列表中每个元素的副本）。
您的功能没有返回任何内容

你需要做这样的事情（就地修改）：

auth.uid

或者像这样（返回副本）：

def show_magicians(magicians):
    for magician in magicians:
        print(magician)

def make_great(magicians):
    for i in range(len(magicians)):
        magicians[i] += " the great"

list_of_magicians = ["Omen", "Carla", "David"]

make_great(list_of_magicians)

print(list_of_magicians)

Answer 3

看起来你需要在make_great方法中实例化另一个数组，并return新数组。

def make_great(magicians):
    """adds the word great to the string"""
    great_magicians = []
    for magician in magicians:
        magician = magician + " the great"
        great_magicians.append(magician)
    return great_magicians

使用for循环修改列表中的字符串？

3 个答案: