[Tutor] if then statements

[Steven D'Aprano]

On Tue, Apr 28, 2015 at 08:24:57PM -0500, Jacqueline G Solis wrote:
> hello,
> 
> I keep getting a syntax error. Could you please explain why that 
> happens and how to correct it.

Syntax errors are sometimes a bit tricky. Usually, they tell you were 
the error is:


py> if (x + 1:
  File "<stdin>", line 1
    if (x + 1:
             ^
SyntaxError: invalid syntax


Notice the blank line immediately before "SyntaxError"? If you look 
carefully, you will see a caret ^ which points to the ":" colon in the 
line before. (In your email, it may not quite line up correctly, but in 
the Python interpreter and the console, they should like up.) That 
should make it obvious that I am missing a closing parenthesis before 
the colon.

But sometimes Python doesn't notice the syntax error until the line 
*after* the actual problem:


py> x = (y + 1
... if x:
  File "<stdin>", line 2
    if x:
        ^
SyntaxError: invalid syntax


The actual problem is that I am missing a round bracket in the previous 
line, but Python doesn't realise it until it gets to the colon.

Does that help?


-- 
Steve