Question

I need to print some stuff only when a boolean variable is set to True. So, after looking at this, I tried with a simple example:

>>> a = 100
>>> b = True
>>> print a if b
  File "<stdin>", line 1
    print a if b
             ^
SyntaxError: invalid syntax  

Same thing if I write print a if b==True.

What am I missing here?

Answer 1

Python does not have a trailing if statement.

There are two kinds of if in Python:

1. if statement:

   if condition: statement
   if condition:
       block
   

2. if expression (introduced in Python 2.5)

   expression_if_true if condition else expression_if_false
   

And note, that both print a and b = a are statements. Only the a part is an expression. So if you write

print a if b else 0

it means

print (a if b else 0)

and similarly when you write

x = a if b else 0

it means

x = (a if b else 0)

Now what would it print/assign if there was no else clause? The print/assignment is still there.

And note, that if you don’t want it to be there, you can always write the regular if statement on a single line, though it’s less readable and there is really no reason to avoid the two-line variant.