How to debug a "multiple statements" error in Python?

Question

Would someone review these lines of code and explain me what's wrong? Why do I get the multiply statements error?

listOrigin = [10, -15, 3, 8, 0, 9, -6, 13, -1, 5]
listMask = []
for item in listOrigin:
    if item > 0:
        listMask.append(1)
    elif item < 0:
        listMask.append(-1)
    else:
        listMask.append(0)

print(listOrigin)
print(listMask)

The error is:

SyntaxError: multiple statements found while compiling a single statement

There is a syntax tool to post a question with correct code / indentation. Review your question and improve the syntax if you want help. — Mathieu, Aug 22 '18 at 12:16
Your indentation doesn't make sense. Does your code actually look like this, or are you uncertain how to paste code in Stack Overflow? — John Coleman, Aug 22 '18 at 12:16
Please fix the indentation in your question to reflect what you're actually running. — roganjosh, Aug 22 '18 at 12:17
@Chris_Rands, yes, my mistake. I didn't realize at first that the indentation was so wrong. — John Anderson, Aug 22 '18 at 12:19
@AbbasOFF, I have started the editing of your code for easier reading. Please continue the editing to show the actual indentation that appears in your code. — John Anderson, Aug 22 '18 at 12:20
I would recommend 1) deleting the code, 2) repasting the code as it actually appears, 3) selecting the newly pasted code in the Stack Overflow editor, and 4) hitting `Ctrl+K` (which is the keyboard shortcut for code formatting). That way others can see what you actually see. — John Coleman, Aug 22 '18 at 12:21

score 2 · Answer 1 · answered Aug 22 '18 at 12:18

As said here, you can't use multiple statements in one shell line.

Uses new line for each statement

listOrigin = [10, -15, 3, 8, 0, 9, -6, 13, -1, 5]
listMask = []
for item in listOrigin:
     if item > 0:
         listMask.append(1)
     elif item < 0:
         listMask.append(-1)
     else:
         listMask.append(0)

print(listOrigin)
print(listMask)

[10, -15, 3, 8, 0, 9, -6, 13, -1, 5]
[1, -1, 1, 1, 0, 1, -1, 1, -1, 1]

score 0 · Answer 2 · answered Aug 22 '18 at 12:21

I take only assumption here. If this is your code:

listOrigin = [10, -15, 3, 8, 0, 9, -6, 13, -1, 5]
listMask = []
for item in listOrigin:
    if item > 0:
        listMask.append(1)
    elif item < 0:
        listMask.append(-1)
    else:
        listMask.append(0)

print(listOrigin)
print(listMask)

Well it works. You need to use multiple lines for the statements. However, you could also write your code like this:

listOrigin = [10, -15, 3, 8, 0, 9, -6, 13, -1, 5]
# Place a 1 if the item is above 0, else a -1. 0 will be flagged as -1.
listMask = [1 if elt > 0 else -1 for elt in listOrigin]
# Place the 0
listMask = [listMask[k] if elt != 0 else 0 for k, elt in enumerate(listOrigin)]

How to debug a "multiple statements" error in Python?

2 Answers2