到达计数器时如何停止打印列表中的项目答案

【问题标题】：How to stop printing items in a list when the counter is reached到达计数器时如何停止打印列表中的项目
【发布时间】：2021-04-06 17:32:09
【问题描述】：

我正在尝试运行一个循环，在列表中打印歌词行，然后在达到可变限制量时停止。虽然我已经尝试了两种不同结果的两种方法，但都不正确。

我遇到的问题：

lyrics = ["I wanna be your endgame", "I wanna be your first string",
          "I wanna be your A-Team", "I wanna be your endgame, endgame"]
lines_of_sanity = 6

#You may modify the lines of code above, but don't move them!
#When you Submit your code, we'll change these lines to
#assign different values to the variables.

#Recall the Earworm problem (3.3.5 Coding Exercise 2). The
#first time, you would still finish printing the entire list
#of lyrics after lines_of_sanity was exceeded.
#
#Revise that code so that you always stop when lines_of_sanity
#is reached. If lines_of_sanity is 6, you would print 6 lines,
#no matter how many lines are in the list. If there are fewer
#than 6 lines in the list, then you'd repeat the list until
#the number of lines is reached.
#
#For example, with the values above, you'd print:
#I wanna be your endgame
#I wanna be your first string
#I wanna be your A-Team
#I wanna be your endgame, endgame
#I wanna be your endgame
#I wanna be your first string
#MAKE IT STOP
#
#That's 6 lines: the entire list once, then the first two lines
#again to reach 6. As before, print MAKE IT STOP when you're
#done.
#
#HINT: There are multiple ways to do this: some involve a small
#change to our earlier answer, others involve a more wholesale
#rewrite. If you're stuck on one, try to think of a totally
#different way!


#Add your code here! Using the initial inputs from above, this
#should print 7 lines: all 4 lines of the list, then the first
#two lines again, then MAKE IT STOP

我的答案及其产生的结果：

counter = 0
while counter <= lines_of_sanity:
    for item in (lyrics):
        print(item)
        counter += len(lyrics)
print("MAKE IT STOP")

我们用歌词 = ["I want to be your endgame", "I want 成为你的第一根弦”、“我想成为你的 A-Team”、“我想成为你的 endgame, endgame"], lines_of_sanity = 6. 我们希望您的代码能够打印这个：

我想成为你的残局我想成为你的第一根弦我想成为你的 A-Team 我想成为你的残局，残局我想成为你的残局我想成为你的第一个字符串 MAKE IT STOP

但是，它打印了这个：

我想成为你的残局我想成为你的第一根弦我想成为你的 A-Team 我想成为你的残局，残局 MAKE IT STOP

在这一点上，它似乎只是比lines_of_sanity少打印一行

或者我的第一次尝试是：

counter = 0
while counter <= lines_of_sanity:
    for item in (lyrics):
        print(item)
        counter += 1
print("MAKE IT STOP")

这似乎将列表中的每个项目打印两次（直到超过 lines_of_sanity），这给了我 8 行

【问题讨论】：

标签： python loops

【解决方案1】：

编辑：在进一步思考后简化了我的答案 - 这是一个用模运算符 % 解决的好问题。取模运算符的作用是返回第一个操作数除以第二个操作数后的余数。虽然不明显，但模运算符非常适合在列表中循环索引。

例子：

lyrics = ["I wanna be your endgame", "I wanna be your first string", 
          "I wanna be your A-Team", "I wanna be your endgame, endgame"]

lines_of_sanity = 6

for i in range(lines_of_sanity):
    print(lyrics[i % len(lyrics)])
        
print("MAKE IT STOP")

输出：

I wanna be your endgame
I wanna be your first string
I wanna be your A-Team
I wanna be your endgame, endgame
I wanna be your endgame
I wanna be your first string
MAKE IT STOP

【讨论】：

【解决方案2】：

    lyrics = ["I wanna be your endgame", "I wanna be your first string",
              "I wanna be your A-Team", "I wanna be your endgame, endgame"]
    lines_of_sanity = 6
    #divide our problem in 2 parts
    #In first part printing all strings of list 
    #if lines_of_sanity more than size of list.
    while lines_of_sanity > len(lyrics):
        for i in lyrics:
            print(i)
        lines_of_sanity -= len(lyrics)
    #In second part printing remaining strings
    for i in range(lines_of_sanity):
        print(lyrics[i])
    
    print("MAKE IT STOP")

【讨论】：

感谢您的回答！虽然这适用于当前歌词，但当代码针对其他歌词进行测试时，例如：我们使用歌词 = [“我不能自己做这一切，不知道”，“我不是超人” ]，lines_of_sanity = 12。我们希望您的代码打印以下内容：IndexError: list index out of range
一切都适合我，也许有些东西与变量不匹配？

【解决方案3】：

      lyrics = ["I wanna be your endgame", "I wanna be your first string",
      "I wanna be your A-Team", "I wanna be your endgame, endgame"]
      lines_of_sanity = 2

      `while lines_of_sanity > len(lyrics):
           for i in lyrics:
               print(i)
           lines_of_sanity -= len(lyrics)

      for i in range(len(lyrics)):
         print(lyrics[i])

      print("MAKE IT STOP")

【讨论】：

正如目前所写，您的答案尚不清楚。请edit 添加其他详细信息，以帮助其他人了解这如何解决所提出的问题。你可以找到更多关于如何写好答案的信息in the help center。

【解决方案4】：

一开始我想太多了，答案很简单

count = 0
while lines_of_sanity > count:
    for line in lyrics:
        count += 1
        if lines_of_sanity >= count:
            print(line)
print("MAKE IT STOP")

您需要设置一个条件来阻止打印当前歌词的所有 4 行。所以我在打印任何行之前添加了一个 if 语句。

【讨论】：