Does Python have a ternary conditional operator?

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If Python does not have a ternary
conditional operator, is it possible to simulate one using other language
constructs?

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class="normal">Answer

Yes, it
was rel="noreferrer" title="[Python-Dev] Conditional Expression
Resolution">added in version 2.5. The expression syntax
is:

a if condition else
            b

First
condition is evaluated, then exactly one of either
a or b is evaluated and returned based
on the title="Boolean data type">Boolean value of
condition. If condition evaluates to
True, then a is evaluated and returned
but b is ignored, or else when b is
evaluated and returned but a is
ignored.

This allows short-circuiting because
when condition is true only a is
evaluated and b is not evaluated at all, but when
condition is false only b is evaluated
and a is not evaluated at
all.

For
example:

>>>
            'true' if True else 'false'
'true'
>>> 'true' if False else
            'false'
'false'

Note
that conditionals are an expression, not a
statement. This means you can't use assignment statements or
pass or other statements within a
conditional
expression:

>>>
            pass if False else x = 3
 File "", line 1


            pass if False else x = 3
 ^
SyntaxError: invalid
            syntax

You can,
however, use conditional expressions to assign a variable like
so:

x = a if True else
            b

Think of
the conditional expression as switching between two values. It is very useful when
you're in a 'one value or another' situation, it but doesn't do much
else.

If you need to use statements, you have to
use a normal if statement instead
of a conditional
expression.

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Keep in mind that it's frowned upon by some
Pythonistas for several
reasons:

• The order of the
  arguments is different from those of the classic condition ? a :
b ternary operator from many other languages (such as C, C++, Go, Perl,
  Ruby, Java, Javascript, etc.), which may lead to bugs when people unfamiliar with
  Python's "surprising" behaviour use it (they may reverse the argument
  order).



• Some find it "unwieldy", since it goes
  contrary to the normal flow of thought (thinking of the condition first and then the
  effects).


• Stylistic reasons. (Although the 'inline
  if' can be really useful, and make your
  script more concise, it really does complicate your
  code)

If you're having
trouble remembering the order, then remember that when read aloud, you (almost) say what
you mean. For example, x = 4 if b > 8 else 9 is read aloud
as x will be 4 if b is greater than 8 otherwise
9.

Official documentation: