Question at position 9 If the missing lines are filled in correctly, the program should remove all comments in a list of strings called code representing lines of a python program. Comments inside code are indicated by the hash character (#). [table]
1 code = [ 'y = 4 # set y to 4',2 'x = y + 3 # set y to 7' ]3 4 i = 05 while i

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Question at position 9 If the missing lines are filled in correctly, the program should remove all comments in a list of strings called code representing lines of a python program. Comments inside code are indicated by the hash character (#). [table]
1  code = [ 'y = 4 # set y to 4',2 'x = y + 3 # set y to 7' ]3 4  i = 05 while i < len(code):6 j = 07 while # ( code WILL go here ):8 if # ( code WILL go here ) == '#':9 # ( code WILL go inside IF )10 j += 111 i += 1
[/table] After execution of the code fragment, the value of code will be:['y = 4', 'x = y + 3']Which of the following options is the correct missing code? (Code filled in has been bolded.) 7  while j < len(code[i]):8 if code[j][i] == '#': 9  code[j] = code[j][:i]7 while j < i:8 if code[j][i] == '#':9 code[j] = code[j][:i]7 while j < len(code[i]):8 if code[i][j] == '#':9 code[i] = code[i][:j]7 while i <= j:8 if code[i][j] == '#':9 code[i] = code[i][:j]Clear my selection

BlackTom AI · Accepted Answer

We start by restating what the question is asking: given a code snippet that processes a list of strings (each string representing a line of Python code), we want to fill in the correct missing lines so that every line has its trailing comment removed, and after execution code becomes ['y = 4', 'x = y + 3']. The presented answer set shows four candidate fills, and we must explain why the first option is the correct choice while the others are not.

Option 1:
7     while j < len(code[i]):
8         if code[i][j] == '#':
9             code[i] = code[i][:j]

Why this works: This option operates on the i-th line (code[i]), scanning characters from index j up to the end of that line. The loop condition uses j < len(code[i]), so j iterates across the characters of the current line. Inside the loop, if a '#' is found at position j, the line is truncated at j, effectively removing the comment portion starting at '#'. After this operation, the line contains only code before the comment, which is precisely the intended behavior for a single line comment removal. The pattern matches the goal of stripping comments from the current line and leaves earlier lines untouched.

Option 2:
7     while j < i:
8         if code[j][i] == '#':
9             code[j] = code[j][:i]

Why this is flawed: The loop bound while j < i uses i as a fixed upper limit, which may prematurely end the inner loop or skip necessary characters. The indexing code[j][i] accesses the i-th character of the j-th line, but the inner loop is intended to examine the characters within a single line, not across different lines. Moreover, slicing code[j] to [:i] truncates the j-th line at i, which inconsistently targets a different line than the one currently being processed. Overall, this misapplies line-wise versus character-wise indexing and would disrupt the intended per-line comment removal.

Option 3:
7     while j < len(code[i]):
8         if code[i][j] == '#':
9             code[i] = code[i][:j]

Why this is not the best choice: At first glance, this appears similar to Option 1, but the difference lies in the exact combination of indices and the impact when the loop continues after removing a '#' at position j. If a '#' is found and code[i] is truncated to code[i][:j], the remainder of the line after j is discarded. If the loop condition relies on the original j index, subsequent iterations may be invalid because the line length has now shortened, potentially causing an index out of range or skipping characters after the cut. Depending on how the loop variable j is updated after truncation (not shown here), this could lead to inconsistent behavior or missed characters in subsequent iterations. In contrast, Option 1 typically handles the control flow more robustly by terminating the line immediately upon encountering '#', and not continuing with a mutated string in a way that could affect the loop’s progression.

Option 4:
7     while i <= j:
8         if code[i][j] == '#':
9             code[i] = code[i][:j]

Why this is incorrect: The loop condition while i <= j mixes two different indices (i and j) in a way that does not reflect a simple left-to-right scan of a single line. The comparison i <= j suggests a relationship between the line index i and the character index j, which does not align with typical per-line comment removal logic where we scan characters within a single line (i fixed, j varying). Accessing code[i][j] is correct for a character in the i-th line, but the outer condition should be about j within the current line, not a relation between i and j. This misalignment makes the loop logic invalid for removing in-line comments in the intended manner.

Summary across options: The core idea is to scan the current line character by character and cut off the line at the first '#', thereby removing the comment portion while preserving the code before the comment. Option 1 does exactly that in a coherent, line-focused way, while Options 2, 3 (depending on update behavior), and 4 introduce indexing or control-flow mismatches that would either operate on the wrong line, risk missing characters, or use a flawed loop condition. Therefore, Option 1 is the correct fill for removing comments from the current line and achieving the target final code.

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