使用 while 循环而不是 for 循环遍历两个列表答案

【问题标题】：iterate over two lists using a while loop instead of a for loop使用 while 循环而不是 for 循环遍历两个列表
【发布时间】：2021-08-14 02:11:38
【问题描述】：

colours = ["red", "green", "blue"]
clothes = ["shirt", "dress", "pants", "jacket", "hat"]


for colour_item in colours:
    for clothes_item in clothes:
        print("I am wearing a ",colour_item," ",clothes_item)

这是我试图更改为 while 循环以产生所有结果的代码，即 15 个结果，我可以使用 while 循环获得的最佳结果是 3。

【问题讨论】：

为什么要为此使用 while 循环？
包括你的while循环代码。

标签： python for-loop while-loop

【解决方案1】：

您可以尝试使用 while 循环，同时为每个列表保留一个索引计数器变量，尽管它本质上只是一个 for 循环：

colours = ["red", "green", "blue"]
clothes = ["shirt", "dress", "pants", "jacket", "hat"]

colorIndex = 0
while(colorIndex < len(colours)):
  clothesIndex = 0
  while(clothesIndex < len(clothes)):
    print("I am wearing a",colours[colorIndex],clothes[clothesIndex])
    clothesIndex += 1
  colorIndex += 1

输出：

I am wearing a red shirt
I am wearing a red dress
I am wearing a red pants
I am wearing a red jacket
I am wearing a red hat
I am wearing a green shirt
I am wearing a green dress
I am wearing a green pants
I am wearing a green jacket
I am wearing a green hat
I am wearing a blue shirt
I am wearing a blue dress
I am wearing a blue pants
I am wearing a blue jacket
I am wearing a blue hat

【讨论】：

【解决方案2】：

如果您愿意做一些数学运算，可以在单个 while 循环中完成。

colours = ["red", "green", "blue"]
clothes = ["shirt", "dress", "pants", "jacket", "hat"]

n = 0
l = len(clothes)

while n < len(colours) * len(clothes):
    print(f"I am wearing a {colours[n // l]}  {clothes[n % l]}")
    n += 1

打印预期的：

I am wearing a red  shirt
I am wearing a red  dress
I am wearing a red  pants
I am wearing a red  jacket
I am wearing a red  hat
I am wearing a green  shirt
I am wearing a green  dress
I am wearing a green  pants
I am wearing a green  jacket
I am wearing a green  hat
I am wearing a blue  shirt
I am wearing a blue  dress
I am wearing a blue  pants
I am wearing a blue  jacket
I am wearing a blue  hat

【讨论】：

我不认为这更有效，它仍然是 O(n^2)
@AnikethMalyala 考虑到 OP 想要打印 m * n 项目 O(n * m) 似乎不可能被击败。这在循环中表达得很清楚len(colours) * len(clothes)
O(m*n)，我的错。我以为你是在暗示你的单数 while 循环比嵌套循环更有效，我的错！
@AnikethMalyala 我可以看到它看起来如何。但是不，只是使代码更短（但可能不是更清晰）。就个人而言，我认为for 循环或itertools.product 是正确的方法。
Fr，在这种情况下使用 for each loop 接缝会更好

【解决方案3】：

colours = ["red", "green", "blue"]
clothes = ["shirt", "dress", "pants", "jacket", "hat"]

i=0
while i<len(colours):
    j=0
    colour_item = colours[i]
    while j<len(clothes):
        clothes_item = clothes[j]
        print("I am wearing a ",colour_item," ",clothes_item)
        j+=1
    i+=1

【讨论】：