Python does not have a trailing if statement.
There are two kinds of if in Python:
if statement:
if condition: statement
if condition:
block
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.
Inline if-else EXPRESSION must always contain else clause, e.g:
a = 1 if b else 0
If you want to leave your ‘a’ variable value unchanged – assing old ‘a’ value (else is still required by syntax demands):
a = 1 if b else a
This piece of code leaves a unchanged when b turns to be False.