将while循环转换为for循环 [英] Converting while loops into for loops

问题描述

将以下while循环转换为for循环.应该编写您的代码，以便不需要更改return语句.您可以在while循环之前更改代码.string_list是一个字符串列表，其中包含至少15个字符串'***'

j=0 
while i<15: 
  if string_list[j] ='***': 
    i +=1 
  j +=1 
return j 

我首先尝试这样做，它说而 i< 15 和 i = i + 1 ，所以我知道我的范围是(0 ... 15)，不包括15所以基本上我们会像 i = range(15)这样，我们会有类似的东西:

I tried doing this first it says while i<15 and i = i+1 so i know i ranges from (0...15) not including 15 so basically we will have like i = range(15) so we will have something like:

for i in range(15):

我不知道那个 j 在做什么.

I don't know what that j is doing there.

推荐答案

我假设您要编写 string_list [j] =='***'而不是 string_list [j] ='***'.我还将假设 i 初始化为 0 .

I will assume you meant to write string_list[j] == '***' instead of string_list[j] ='***'. I will also assume i is initialised to 0.

i, j = 0, 0 
while i < 15: 
  if string_list[j] == '***': 
    i += 1 
  j += 1 
return j 

第一步是了解循环的实际作用.它遍历 string_list 元素，并且每次遇到'***'时， i 都会递增.当 i 达到 15 时，循环将终止，并且由于前提是 string_list 包含至少15个'**的副本*'我们确实希望循环会终止.

The first step is to understand what the loop is actually doing. It is iterating through string_list elements, and every time an '***' is encountered, i is incremented. The loop will terminate when i reaches 15, and since a precondition was given that string_list contains at least 15 copies of '***' we do expect the loop should terminate.

当循环终止时， i 等于 15 ，而 j 只会计算列表中的元素数量，直到这点.

When the loop terminates, i will be equal to 15 and j will simply have counted the number of elements in the list up until this point.

因此，从头开始，您可以尝试像这样进行迭代:

So to start you off, you could try iterating like this:

for s in string_list:
  if s == `***`:
    # keep track of how many times this has happened
    # break if you've seen it happen 15 times
  j += 1
return j

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