使用for循环在列表中查找用户定义的项

Question

我有以下代码：

def main():
    list=["chocolate", "jelly", "biscuits"]
    eat=input("What do you wanna eat?")
    for i in list:
        if list.index(eat)==eat:        
            break
        else:
            break

    print("We have that in tray:", list.index(eat))
main()

在VB.Net中，这在For循环中很容易实现，这是一种惯用的方法。为什么不在这里？另外，这并不是stackoverflow的另一个问题的重复，在这个问题中，用户提供了做类似事情的替代方法/pythonic建议

出于教学目的，我需要使用For循环，并更正上面给出的结构

如果用户输入的不是列表中的内容，我如何添加条件逻辑来打印“该项目不在列表中”。我正在寻找最简单的修复我的原始代码

我确实尝试了以下方法，但结果是出现了逻辑错误。有一个解决方案

试试#1：

def main():
    list=["chocolate", "jelly", "biscuits"]
    eat=input("What do you wanna eat?")
    for i in list:
        if list.index(eat)==eat:        
            break
        else:
            print("that is not in the list")

    print("We have that in tray:", list.index(eat))
main()

错误：

>>> 
What do you wanna eat?jelly
that is not in the list
that is not in the list
that is not in the list
We have that in tray: 1
>>> 

尝试2

def main():
    list=["chocolate", "jelly", "biscuits"]
    eat=input("What do you wanna eat?")
    for i in list:
        if list.index(eat)==eat:        
            break
        else:
            break
    print("that is not in the list")

    print("We have that in tray:", list.index(eat))
main()

错误：

>>> 
What do you wanna eat?jelly
that is not in the list
We have that in tray: 1
>>> 

试试#3：

def main():
    list=["chocolate", "jelly", "biscuits"]
    eat=input("What do you wanna eat?")
    for i in list:
        if list.index(eat)==eat:        
            break
        elif list.index(eat)!=eat:
            print("that is not in the list")

    print("We have that in tray:", list.index(eat))
main()

错误：

>>> 
What do you wanna eat?jelly
that is not in the list
that is not in the list
that is not in the list
We have that in tray: 1
>>> 

Answer 1

在这里：

def main():
    list=["chocolate", "jelly", "biscuits"]
    eat=input("What do you wanna eat?")
    for element in list:
        index = list.index(element)
        if element == eat:
          print("We have that in tray:", index)
          break
          # If the element is found, then print the message and stop the loop

        elif index == len(list) - 1:
          # Index starts form 0, then if you have a list with n elements
          # and you reach the element with index n-1, you have reached
          # the last element.
          print("that is not in the list")
          # if the element is the last in the list, and it's not
          # equal to the user input, then the user input is not in the
          # list. Print the error message.

main()

使用enumerate

def main():
    list=["chocolate", "jelly", "biscuits"]
    eat=input("What do you wanna eat?")
    for index,element in enumerate(list):
        if element == eat:
          print("We have that in tray:", index)
          break
        elif index == len(list) - 1:
          print("that is not in the list")

main()

Answer 2

def main():
    list=["chocolate", "jelly", "biscuits"]
    eat=input("What do you wanna eat?")
if eat in list:
    print("We have that in tray:", list.index(eat))
else:
    print("That is not in the list")

main()