error when trying to use pass keyword in one line if statement

Question

stumped that this works:

if 5 % 2 == 0:
        print "no remainder"
else:
        pass

but not this:

print "no remainder" if 5% 2 == 0 else pass

SyntaxError: invalid syntax

Answer 1

The latter is not an if statement, rather an expression (I mean, print is a statement, but the rest is being interpreted as an expression, which fails). Expressions have values. pass doesn't, because it's a statement.

You may be seeing it as two statements (print or pass), but the interpreter sees it differently:

expr = "no remainder" if 5% 2 == 0 else pass
print expr

and the first line is problematic because it mixes an expression and a statement.

A one-line if statement is a different thing:

if 5 % 2 == 0: print "no remainder"

this can be called a one-line if statement.

P.S. Ternary expressions are referred to as "conditional expressions" in the official docs.

A ternary expression uses the syntax you tried to use, but it needs two expressions and a condition (also an expression):

expr1 if cond else expr2

and it takes the value of expr1 if bool(cond) == True and expr2 otherwise.