Question

我只是在学习Python，并且正在尝试将范围与枚举结合起来。我尝试了一些如：

students = ("James","John","Robert","Michael","William","David","Richard","Joseph","Thomas","Charles","Christopher","Daniel","Matthew","Anthony","Donald","Mark","Paul","Steven","Andrew","Kenneth","George","Joshua","Kevin","Brian","Edward","Mary","Patricia","Jennifer","Elizabeth","Linda","Barbara","Susan","Jessica","Margaret","Sarah","Karen","Nancy","Betty","Lisa","Dorothy","Sandra","Ashley","Kimberly","Donna","Carol","Michelle","Emily","Amanda","Helen","Melissa")
print("The gold medal goes to:",students[0])
print("The silver medal goes to:",students[1])
print("The bronze medal goes to:",students[2])
print("All winners in order:")
for index, student in enumerate(students):
    for students in range(3,51):
        place=str(index+1)
        print(place,student.title())

这给了我一个错误，我试过这个：

.psuedo-background-img-container {
  position: relative;
  width:400px;
  height: 200px;
}
.psuedo-background-img {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

只打印每个名字50次。我只是一名学生，所以感谢任何帮助！

Answer 1

您的示例不需要使用range。为了了解您的摘要中出了什么问题，请考虑以下代码：

>>> for index, student in enumerate(students):
...     print(index, student)
...

此打印：

0 James
1 John
2 Robert
...
49 Melissa

enumerate具有两个参数：

数组
可选地，第一个用作索引的数字（如果没有给出，则为零）。

它返回两件事：

数组所有索引的列表（即从零到len(your_array)-1）
数组本身

请注意您的第一个代码段如何包含for index, student in enumerate(students in range(3,51)):，尤其是students in range(3,51)表达式。因为 that 并不紧跟for的前面，所以它没有像您希望的那样遍历范围，而是将其作为条件。而且由于students是您代码中的元组，因此 not 不在range(3,51)内，并且此表达式将返回False。由于无法调用enumerate(False)，因为False不是数组，所以会收到错误TypeError: 'bool' object is not iterable。

在第二个片段中，您遍历了整个枚举，但是每个名称实际上被打印了48次（51-3 = 48），而被多次打印的原因是因为内部for语句具有index和student元素，但是每次将students设置为3、4，以50为上限（但不包括51）时，都会打印它们。顺便说一句，请不要在此处重新分配students，否则它将用数字代替您的学生组。

相反，您应该切出所需的学生元组的一部分，并指定要打印的第一个索引，然后将其作为参数传递给enumerate，因此，您的情况是：enumerate(students[3:], 3)。特别是，您以此打印的索引将从三个开始，不是为零。

然后您的代码变为：

students = ("James","John","Robert","Michael","William","David","Richard","Joseph","Thomas","Charles","Christopher","Daniel","Matthew","Anthony","Donald","Mark","Paul","Steven","Andrew","Kenneth","George","Joshua","Kevin","Brian","Edward","Mary","Patricia","Jennifer","Elizabeth","Linda","Barbara","Susan","Jessica","Margaret","Sarah","Karen","Nancy","Betty","Lisa","Dorothy","Sandra","Ashley","Kimberly","Donna","Carol","Michelle","Emily","Amanda","Helen","Melissa")
print("The gold medal goes to:",students[0])
print("The silver medal goes to:",students[1])
print("The bronze medal goes to:",students[2])
print("All winners in order:")
for index, student in enumerate(students[3:], 3):
    place=str(index+1)
    print(place,student.title())

这将打印预期的输出：

4 Michael
5 William
6 David
...
50 Melissa

枚举与范围相结合

1 个答案: