if语句中的Python语法错误

Question

I'm stucked with a Python if-statement. I finished pretty much everything but when running my progarmm, it gives my an syntax error in the first line: I'm so sure I did everything right but as I'm very new to Python and programming at all, it might just be a very foolish mistake... Thanks for helping guys!

if a == 2:   
StartDeckNeighbourright = StartDeck[a + 1]
StartDeckNeighbourright2 = StartDeck[a + 2]

Answer 1

If this isn't the IndentationError that jramirez's answer fixes, but rather an actual SyntaxError , it's probably a problem with the line before the if statement.

In Python, you can continue an expression across multiple lines, as long as the expression is inside parentheses. So, if you accidentally leave off a ) at the end of a function call, or a tuple, or anything else, you often get a mysterious SyntaxError on the next line. For example, this code:

foo = (1, 2
if a == 2:
    pass

… will give this error:

    if a == 2:
             ^
SyntaxError: invalid syntax

And just adding another comma moves the error somewhere different!

foo = (1, 2,
if a == 2:
    pass

    if a == 2:
     ^
SyntaxError: invalid syntax

Why? Well, even when you understand exactly what these errors mean, they still aren't very helpful. So first, remember:

If you get a SyntaxError on a perfectly valid line, look for a missing ) (or ] or } , or an extra \\ , or a few other special cases) on the line above.

And if you can get an editor that helps you match up parentheses and brackets, it will make this problem much less likely. (For example, with emacs, at least the way I have it set up, it'll automatically try to indent the if line 7 characters for me, and if I "fix" it it'll fight back against me, and eventually it'll be hard not to notice something is wrong. Then I point at the first ( and it tells me it's unmatched.)

But if you want to know, here goes:

The first version builds a tuple with the value 1 , then a value starting with 2 and continuing onto the next line. 2 if a == 2 is a perfectly good beginning for a ternary if expression, but 2 if a == 2: is not; the colon forces it to be an if statement, and you can't put a statement in the middle of an expression.

The second version builds a tuple with the value 1 , the value 2 , and more values continuing on the next line. if cannot be the start of any valid expression, so you get the SyntaxError earlier. But still not early enough to be useful, of course.

Answer 2

You should post the error you are seeing, however I think all you need is indentation after the if statment

if a == 2:   
    StartDeckNeighbourright = StartDeck[a + 1]
    StartDeckNeighbourright2 = StartDeck[a + 2]
---- four spaces of indentation

Answer 3

In python You must use Indentation:

if a == 2:
    StartDeckNeighbourright = StartDeck[a + 1]
    StartDeckNeighbourright2 = StartDeck[a + 2]