Yes, it wasadded in version 2.5. The expression syntax is:

a if condition else b

Firstcondition is evaluated, then exactly one of eithera orb is evaluated and returned based on theBoolean value ofcondition. Ifcondition evaluates toTrue, thena is evaluated and returned butb is ignored, or else whenb is evaluated and returned buta is ignored.

This allows short-circuiting because whencondition is true onlya is evaluated andb is not evaluated at all, but whencondition is false onlyb is evaluated anda is not evaluated at all.

For example:

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

Note that conditionals are anexpression, not astatement. This means you can't usestatements such aspass, or assignments with= (or "augmented" assignments like+=), within a conditionalexpression:

>>> pass if False else pass  File "<stdin>", line 1    pass if False else pass         ^SyntaxError: invalid syntax>>> # Python parses this as `x = (1 if False else y) = 2`>>> # The `(1 if False else x)` part is actually valid, but>>> # it can't be on the left-hand side of `=`.>>> x = 1 if False else y = 2  File "<stdin>", line 1SyntaxError: cannot assign to conditional expression>>> # If we parenthesize it instead...>>> (x = 1) if False else (y = 2)  File "<stdin>", line 1    (x = 1) if False else (y = 2)       ^SyntaxError: invalid syntax

(In 3.8 and above, the:= "walrus" operator allows simple assignment of valuesas an expression, which is then compatible with this syntax. But please don't write code like that; it will quickly become very difficult to understand.)

Similarly, because it is an expression, theelse part ismandatory:

# Invalid syntax: we didn't specify what the value should be if the # condition isn't met. It doesn't matter if we can verify that# ahead of time.a if True

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

x = a if True else b

Or for example to return a value:

# Of course we should just use the standard library `max`;# this is just for demonstration purposes.def my_max(a, b):    return a if a > b else b

Think of the conditional expression as switching between two values. We can use it when we are in a 'one value or another' situation, where we willdo the same thing with the result, regardless of whether the condition is met. We use the expression to compute the value, and then do something with it. If you need todo something different depending on the condition, then use a normalifstatement instead.

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 classiccondition ? a : b ternary operator from many other languages (such asC,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 'inlineif' can bereally 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 asx will be 4 if b is greater than 8 otherwise 9.

Official documentation:

• Conditional expressions
• Is there an equivalent of C’s ”?:” ternary operator?

You can index into a tuple:

(falseValue, trueValue)[test]

test needs to returnTrue orFalse.
It might be safer to always implement it as:

(falseValue, trueValue)[test == True]

or you can use the built-inbool() to assure aBoolean value:

(falseValue, trueValue)[bool(<expression>)]

For versions prior to 2.5, there's the trick:

[expression] and [on_true] or [on_false]

It can give wrong results whenon_true has a false Boolean value.¹

Although it does have the benefit of evaluating expressions left to right, which is clearer in my opinion.

_{1.Is there an equivalent of C’s ”?:” ternary operator?}

<expression 1>if<condition>else<expression 2>

a = 1b = 21 if a > b else -1 # Output is -11 if a > b else -1 if a < b else 0# Output is -1

Fromthe documentation:

Conditional expressions (sometimes called a “ternary operator”) have the lowest priority of all Python operations.

The expressionx if C else y first evaluates the condition,C (not x); ifC is true,x is evaluated and its value is returned; otherwise,y is evaluated and its value is returned.

SeePEP 308 for more details about conditional expressions.

New since version 2.5.

An operator for a conditional expression in Python was added in 2006 as part ofPython Enhancement Proposal 308. Its form differs from common?: operator and it looks like this:

<expression1> if <condition> else <expression2>

which is equivalent to:

if <condition>: <expression1> else: <expression2>

Here is an example:

result = x if a > b else y

Another syntax which can be used (compatible with versions before 2.5):

result = (lambda:y, lambda:x)[a > b]()

where operands arelazily evaluated.

Another way is by indexing a tuple (which isn't consistent with the conditional operator of most other languages):

result = (y, x)[a > b]

or explicitly constructed dictionary:

result = {True: x, False: y}[a > b]

Another (less reliable), but simpler method is to useand andor operators:

result = (a > b) and x or y

however this won't work ifx would beFalse.

A possible workaround is to makex andy lists or tuples as in the following:

result = ((a > b) and [x] or [y])[0]

or:

result = ((a > b) and (x,) or (y,))[0]

If you're working with dictionaries, instead of using a ternary conditional, you can take advantage ofget(key, default), for example:

shell = os.environ.get('SHELL', "/bin/sh")

^{Source:?: in Python at Wikipedia}

Unfortunately, the

(falseValue, trueValue)[test]

solution doesn't have short-circuit behaviour; thus bothfalseValue andtrueValue are evaluated regardless of the condition. This could be suboptimal or even buggy (i.e. bothtrueValue andfalseValue could be methods and have side effects).

One solution to this would be

(lambda: falseValue, lambda: trueValue)[test]()

(execution delayed until the winner is known ;)), but it introduces inconsistency between callable and non-callable objects. In addition, it doesn't solve the case when using properties.

And so the story goes - choosing between three mentioned solutions is a trade-off between having the short-circuit feature, using at least Python 2.5 (IMHO, not a problem anymore) and not being prone to "trueValue-evaluates-to-false" errors.

For Python 2.5 and newer there is a specific syntax:

[on_true] if [cond] else [on_false]

In older Pythons, a ternary operator is not implemented but it's possible to simulate it.

cond and on_true or on_false

Though there is a potential problem, which is ifcond evaluates toTrue andon_true evaluates toFalse thenon_false is returned instead ofon_true. If you want this behaviour the method is OK, otherwise use this:

{True: on_true, False: on_false}[cond is True] # is True, not == True

which can be wrapped by:

def q(cond, on_true, on_false)    return {True: on_true, False: on_false}[cond is True]

and used this way:

q(cond, on_true, on_false)

It is compatible with all Python versions.

You might often find

cond and on_true or on_false

but this leads to a problem when on_true == 0

>>> x = 0>>> print x == 0 and 0 or 11>>> x = 1>>> print x == 0 and 0 or 11

Where you would expect this result for a normal ternary operator:

>>> x = 0>>> print 0 if x == 0 else 10>>> x = 1>>> print 0 if x == 0 else 11

Does Python have a ternary conditional operator?

Yes. From thegrammar file:

test: or_test ['if' or_test 'else' test] | lambdef

The part of interest is:

or_test ['if' or_test 'else' test]

So, a ternary conditional operation is of the form:

expression1 if expression2 else expression3

expression3 will be lazily evaluated (that is, evaluated only ifexpression2 is false in a boolean context). And because of the recursive definition, you can chain them indefinitely (though it may considered bad style.)

expression1 if expression2 else expression3 if expression4 else expression5 # and so on

A note on usage:

Note that everyif must be followed with anelse. People learning list comprehensions and generator expressions may find this to be a difficult lesson to learn - the following will not work, as Python expects a third expression for an else:

[expression1 if expression2 for element in iterable]#                          ^-- need an else here

which raises aSyntaxError: invalid syntax.So the above is either an incomplete piece of logic (perhaps the user expects a no-op in the false condition) or what may be intended is to useexpression2 as a filter - notes that the following is legal Python:

[expression1 for element in iterable if expression2]

expression2 works as a filter for the list comprehension, and isnot a ternary conditional operator.

Alternative syntax for a more narrow case:

You may find it somewhat painful to write the following:

expression1 if expression1 else expression2

expression1 will have to be evaluated twice with the above usage. It can limit redundancy if it is simply a local variable. However, a common and performant Pythonic idiom for this use-case is to useor's shortcutting behavior:

expression1 or expression2

which is equivalent in semantics. Note that some style-guides may limit this usage on the grounds of clarity - it does pack a lot of meaning into very little syntax.

One of the alternatives to Python'sconditional expression

"yes" if boolean else "no"

is the following:

{True: "yes", False: "no"}[boolean]

which has the following nice extension:

{True: "yes", False: "no", None: "maybe"}[boolean_or_none]

The shortest alternative remains

("no", "yes")[boolean]

which works becauseissubclass(bool, int).

Careful, though: the alternative to

yes() if boolean else no()

isnot

(no(), yes())[boolean]  # bad: BOTH no() and yes() are called

but

(no, yes)[boolean]()

This works fine as long asno andyes are to be called with exactly the same parameters. If they are not, like in

yes("ok") if boolean else no()  # (1)

or in

yes("ok") if boolean else no("sorry")  # (2)

then a similar alternative either does not exist (1) or is hardly viable (2). (In rare cases, depending on the context, something like

msg = ("sorry", "ok")[boolean](no, yes)[boolean](msg)

could make sense.)

_{Thanks to Radek Rojík for his comment}

Addendum:

A special case of boolean indexing is when you need a single character. E.g.:

sign = '+-'[n < 0]

And finally, the plurals:

print(f"total: {n} item{'s'[n==1:]}")

As already answered, yes, there is a ternary operator in Python:

<expression 1> if <condition> else <expression 2>

In many cases<expression 1> is also used as Boolean evaluated<condition>. Then you can useshort-circuit evaluation.

a = 0b = 1# Instead of this:x = a if a else b# Evaluates as 'a if bool(a) else b'# You could use short-circuit evaluation:x = a or b

One big pro of short-circuit evaluation is the possibility of chaining more than two expressions:

x = a or b or c or d or e

When working with functions it is more different in detail:

# Evaluating functions:def foo(x):    print('foo executed')    return xdef bar(y):    print('bar executed')    return ydef blubb(z):    print('blubb executed')    return z# Ternary Operator expression 1 equals to Falseprint(foo(0) if foo(0) else bar(1))''' foo and bar are executed oncefoo executedbar executed1'''# Ternary Operator expression 1 equals to Trueprint(foo(2) if foo(2) else bar(3))''' foo is executed twice!foo executedfoo executed2'''# Short-circuit evaluation second equals to Trueprint(foo(0) or bar(1) or blubb(2))''' blubb is not executedfoo executedbar executed1'''# Short-circuit evaluation third equals to Trueprint(foo(0) or bar(0) or blubb(2))'''foo executedbar executedblubb executed2'''# Short-circuit evaluation all equal to Falseprint(foo(0) or bar(0) or blubb(0))''' Result is 0 (from blubb(0)) because no value equals to Truefoo executedbar executedblubb executed0'''

PS: Of course, a short-circuit evaluation is not a ternary operator, but often the ternary is used in cases where the short circuit would be enough. It has a better readability and can be chained.

Simulating the Python ternary operator.

For example

a, b, x, y = 1, 2, 'a greather than b', 'b greater than a'result = (lambda:y, lambda:x)[a > b]()

Output:

'b greater than a'

a if condition else b

Just memorize this pyramid if you have trouble remembering:

     condition  if           elsea                   b

Vinko Vrsalovic's answer is good enough. There is only one more thing:

Note that conditionals are anexpression, not astatement. This means you can't use assignment statements orpass or otherstatements within a conditionalexpression

Walrus operator in Python 3.8

After thewalrus operator was introduced in Python 3.8, something changed.

(a := 3) if True else (b := 5)

givesa = 3 andb is not defined,

(a := 3) if False else (b := 5)

givesa is not defined andb = 5, and

c = (a := 3) if False else (b := 5)

givesc = 5,a is not defined andb = 5.

Even if this may be ugly,assignments can be doneinside conditional expressions after Python 3.8. Anyway, it is still better to use normalifstatement instead in this case.

The ternary conditional operator simply allows testing a condition in a single line replacing the multiline if-else making the code compact.

Syntax:

[on_true] if [expression] else [on_false]

1- Simple Method to use ternary operator:

# Program to demonstrate conditional operatora, b = 10, 20# Copy value of a in min if a < b else copy bmin = a if a < b else bprint(min)  # Output: 10

2- Direct Method of using tuples, Dictionary, and lambda:

# Python program to demonstrate ternary operatora, b = 10, 20# Use tuple for selecting an itemprint( (b, a) [a < b] )# Use Dictionary for selecting an itemprint({True: a, False: b} [a < b])# lambda is more efficient than above two methods# because in lambda  we are assure that# only one expression will be evaluated unlike in# tuple and Dictionaryprint((lambda: b, lambda: a)[a < b]()) # in output you should see three 10

3- Ternary operator can be written as nested if-else:

# Python program to demonstrate nested ternary operatora, b = 10, 20print ("Both a and b are equal" if a == b else "a is greater than b"        if a > b else "b is greater than a")

Above approach can be written as:

# Python program to demonstrate nested ternary operatora, b = 10, 20if a != b:    if a > b:        print("a is greater than b")    else:        print("b is greater than a")else:    print("Both a and b are equal")# Output: b is greater than a

You can do this:

[condition] and [expression_1] or [expression_2];

Example:

print(number%2 and "odd" or "even")

This would print "odd" if the number is odd or "even" if the number is even.

The result: If condition is true, exp_1 is executed, else exp_2 is executed.

Note: 0, None, False, emptylist, and emptyString evaluates as False.

And any data other than 0 evaluates to True.

Here's how it works:

If the condition [condition] becomes "True", then expression_1 will be evaluated, but not expression_2.

If we "and" something with 0 (zero), the result will always to be false. So in the below statement,

0 and exp

The expressionexp won't be evaluated at all since "and" with 0 will always evaluate to zero and there is no need to evaluate the expression. This is how the compiler itself works, in all languages.

In

1 or exp

the expressionexp won't be evaluated at all since "or" with 1 will always be 1. So it won't bother to evaluate the expression exp since the result will be 1 anyway (compiler optimization methods).

But in case of

True and exp1 or exp2

The second expression exp2 won't be evaluated sinceTrue and exp1 would be True when exp1 isn't false.

Similarly in

False and exp1 or exp2

The expressionexp1 won't be evaluated since False is equivalent to writing 0 and doing "and" with 0 would be 0 itself, but after exp1 since "or" is used, it will evaluate the expression exp2 after "or".

Note:- This kind of branching using "or" and "and" can only be used when the expression_1 doesn't have a Truth value of False (or 0 or None or emptylist [ ] or emptystring ' '.) since if expression_1 becomes False, then the expression_2 will be evaluated because of the presence "or" between exp_1 and exp_2.

In case you still want to make it work for all the cases regardless of what exp_1 and exp_2 truth values are, do this:

[condition] and ([expression_1] or 1) or [expression_2];

More a tip than an answer (I don't need to repeat the obvious for the hundredth time), but I sometimes use it as a one-liner shortcut in such constructs:

if conditionX:    print('yes')else:    print('nah')

, becomes:

print('yes') if conditionX else print('nah')

Some (many :) may frown upon it as unpythonic (even, Ruby-ish :), but I personally find it more natural - i.e., how you'd express it normally, plus a bit more visually appealing in large blocks of code.

Many programming languages derived fromC usually have the following syntax of the ternary conditional operator:

<condition> ? <expression1> : <expression2>

At first, the Python'sbenevolent dictator for life (I meanGuido van Rossum, of course) rejected it (as non-Pythonic style), since it's quite hard to understand for people not used to C language. Also, the colon sign: already has many uses in Python. AfterPEP 308 was approved, Python finally received its own shortcut conditional expression (what we use now):

<expression1> if <condition> else <expression2>

So, firstly it evaluates the condition. If it returnsTrue,expression1 will be evaluated to give the result, otherwiseexpression2 will be evaluated. Due tolazy evaluation mechanics – only one expression will be executed.

Here are some examples (conditions will be evaluated from left to right):

pressure = 10print('High' if pressure < 20 else 'Critical')# Result is 'High'

Ternary operators can be chained in series:

pressure = 5print('Normal' if pressure < 10 else 'High' if pressure < 20 else 'Critical')# Result is 'Normal'

The following one is the same as previous one:

pressure = 5if pressure < 20:    if pressure < 10:        print('Normal')    else:        print('High')else:    print('Critical')# Result is 'Normal'

Yes, Python have a ternary operator, here is the syntax and an example code to demonstrate the same :)

#[On true] if [expression] else[On false]# if the expression evaluates to true then it will pass On true otherwise On falsea = input("Enter the First Number ")b = input("Enter the Second Number ")print("A is Bigger") if a>b else print("B is Bigger")

Python has a ternary form for assignments; however there may be even a shorter form that people should be aware of.

It's very common to need to assign to a variable one value or another depending on a condition.

>>> li1 = None>>> li2 = [1, 2, 3]>>>>>> if li1:...     a = li1... else:...     a = li2...>>> a[1, 2, 3]

^ This is the long form for doing such assignments.

Below is the ternary form. But this isn't the most succinct way - see the last example.

>>> a = li1 if li1 else li2>>>>>> a[1, 2, 3]>>>

With Python, you can simply useor for alternative assignments.

>>> a = li1 or li2>>>>>> a[1, 2, 3]>>>

The above works sinceli1 isNone and the interpreter treats that as False in logic expressions. The interpreter then moves on and evaluates the second expression, which is notNone and it's not an empty list - so it gets assigned toa.

This also works with empty lists. For instance, if you want to assigna whichever list has items.

>>> li1 = []>>> li2 = [1, 2, 3]>>>>>> a = li1 or li2>>>>>> a[1, 2, 3]>>>

Knowing this, you can simplify such assignments whenever you encounter them. This also works with strings and other iterables. You could assigna whichever string isn't empty.

>>> s1 = ''>>> s2 = 'hello world'>>>>>> a = s1 or s2>>>>>> a'hello world'>>>

I always liked the C ternary syntax, but Python takes it a step further!

I understand that some may say this isn't a good stylistic choice, because it relies on mechanics that aren't immediately apparent to all developers. I personally disagree with that viewpoint. Python is a syntax-rich language with lots of idiomatic tricks that aren't immediately apparent to the dabbler. But the more you learn and understand the mechanics of the underlying system, the more you appreciate it.

Other answers correctly talk about the Python ternary operator. I would like to complement by mentioning a scenario for which the ternary operator is often used, but for which there is a better idiom. This is the scenario of using a default value.

Suppose we want to useoption_value with a default value if it is not set:

run_algorithm(option_value if option_value is not None else 10)

or, ifoption_value is never set to a falsy value (0,"", etc.), simply

run_algorithm(option_value if option_value else 10)

However, in this case an ever better solution is simply to write

run_algorithm(option_value or 10)

The syntax for the ternary operator in Python is:

[on_true] if [expression] else [on_false]

Using that syntax, here is how we would rewrite the code above using Python’s ternary operator:

game_type = 'home'shirt = 'white' if game_type == 'home' else 'green'

It's still pretty clear, but much shorter. Note that the expression could be any type of expression, including a function call, that returns a value that evaluates to True or False.

Pythonic way of doing the things:

"true" if var else "false"

But there always exists a different way of doing a ternary condition too:

"true" and var or "false"

There are multiple ways. The simplest one is to use the condition inside the "print" method.

You can use

print("Twenty" if number == 20 else "Not twenty")

Which is equivalent to:

if number == 20:    print("Twenty")else:    print("Not twenty")

In this way, more than two statements are also possible to print. For example:

if number == 20:    print("Twenty")elif number < 20:    print("Lesser")elif 30 > number > 20:    print("Between")else:    print("Greater")

can be written as:

print("Twenty" if number == 20 else "Lesser" if number < 20 else "Between" if 30 > number > 20 else "Greater")

Yes, Python has a ternary operator, but it's different from C-syntax-like programming languages, where you'd do this:

condition ? value_if_true : value_if_false

Whereas Python follows this syntax:

value_if_true if condition else value_if_false

For example, in C++:

even_or_odd = x % 2 == 0 ? "even" : "odd";

Versus Python where you'd use:

even_or_odd = "even" if x % 2 == 0 else "odd"

Theif else-if version can be written as:

sample_set="train" if "Train" in full_path else ("test" if "Test" in full_path else "validation")

Yes, Python has a ternary conditional operator, also known as the conditional expression or the ternary operator. The syntax of the ternary operator in Python is:

value_if_true if condition else value_if_false

Here's an example to illustrate its usage:

x = 5result = "Even" if (x % 2 == 0) else "Odd"print(result)

In this example, the condition x % 2 == 0 checks if x is divisible by 2. If the condition is True, the value "Even" is assigned to the variable result. Otherwise, the value "Odd" is assigned. The output will be:

Odd

It is a good idea to use parenthesis, in order to increase readability, when working with medium complexity operations:

"Even" if (x % 2 == 0) else "Odd"

Instead of:

"Even" if x % 2 == 0 else "Odd"

The ternary operator is a concise way to write simple conditional expressions in a single line. It can be particularly useful when assigning values or constructing expressions based on conditions. However, for more complex conditions or longer expressions, if possible it's generally better to use if-else statements for improved readability.

For the Python 2.5 and above we can use the following[value] if [expression] else [elsevalue] to build a switch statement as follows:

     [value1] if [expression1] \else [value2] if [expression2] \else [value3] if [expression3] \else ... \else [elsevalue]

For example:

# input temperature in celciustemperature = 133# determine the water state based on the input temperaturewater_state =      "Ice"    if temp <   0 \              else "Liquid" if temp < 100 \              else "Steam"

For pre-Python 2.5 and as an interesting variation to James Brady's answerhttps://stackoverflow.com/a/394887/881441 one can extend this pattern to implement switch by chaining[expression] and [value] as follows:

   [expression1] and [value1] \or [expression2] and [value2] \or [expression3] and [value3] \or ... \or [elsevalue]

For example:

# input temperature in celciustemperature = 133# determine the water state based on the input temperaturewater_state = temperature <   0 and "Ice" \           or temperature < 100 and "Liquid" \           or "Steam"

As per James Brady's assessment and in this linkIs there an equivalent of C's "?:" ternary operator? this idiom is unsafe and can give the wrong results if any of the right-hand side values are falsy (are equivalent to a false boolean value).

A neat way to chain multiple operators:

f = lambda x,y: 'greater' if x > y else 'less' if y > x else 'equal'array = [(0,0),(0,1),(1,0),(1,1)]for a in array:  x, y = a[0], a[1]  print(f(x,y))# Output is:#   equal,#   less,#   greater,#   equal

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