Performance of ternary operator vs if-else statement

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Note: It's true that this question has been answered for many other languages. However, I could not find an answer for Python, so do not mark as duplicate.

Is there a difference in performance between the if-else statement and the ternary operator in Python?

I doubt there is a performance difference. They compile to equivalent sequences of bytecodes:

>>> def f():
...   return a if b else c
...
>>> dis.dis(f)
  2           0 LOAD_GLOBAL              0 (b)
              2 POP_JUMP_IF_FALSE        8
              4 LOAD_GLOBAL              1 (a)
              6 RETURN_VALUE
        >>    8 LOAD_GLOBAL              2 (c)
             10 RETURN_VALUE
>>> def g():
...   if b:
...     return a
...   else:
...     return c
...
>>> dis.dis(g)
  2           0 LOAD_GLOBAL              0 (b)
              2 POP_JUMP_IF_FALSE        8

  3           4 LOAD_GLOBAL              1 (a)
              6 RETURN_VALUE

  5     >>    8 LOAD_GLOBAL              2 (c)
             10 RETURN_VALUE
             12 LOAD_CONST               0 (None)
             14 RETURN_VALUE

As with most performance questions, the answer is to measure.

Ternary operators vs if-else statements | by jraleman, You have probably seen a ternary operator (also known as a conditional expression) before in a source file, or somewhere else. In C, and in a� I agree with @Niklas, but if you really don't like ternary operator and you don't care about truly trivial performance differences, you could initialize the variable to the default value (presumably 5), and only use an "if" without an "else" to reassign it.

From some testing on Python 3.6.1, it seems like the full statement is faster.

My Results:

>>> timeit.timeit("""3 if True else 8""")
0.012174860001323395
>>> timeit.timeit("""3 if False else 8""")
0.019092951000857283
>>> timeit.timeit("""if True:
...     3
... else:
...     8""")
0.009110345999943092
>>> timeit.timeit("""if False:
...     3
... else:
...     8""")
0.00877297099941643

Prettiness of ternary operator vs. if statement, Performance. The ternary operator shouldn't differ in performance from a well- written equivalent if / else statement they may well resolve to the same� It is similar to “if else” statement. For beginners, the difference between ternary or conditional operator and if else statement is a bit difficult to understand. This page explains the difference between the ternary or conditional operator and the if-elseif-else statement. Data based decision making is very important in programming languages.

Here're my tests in IPython 7.2.0 (which has %timeit, a built-in timing method that makes it extremely easy to measure executions. By default it makes 7 runs and 100 million loops each, so the results should usually be valid) used by PyCharm 2018.3.4 Community Edition x64, running CPython 3.7.2 x64. The OS is Window$ 10.0.17134 Enterprise x64:

##The 1st 2 are without quoting the statement to see how it affects the test.
%timeit 3 if True else 8
14.7 ns ± 0.319 ns per loop (mean ± std. dev. of 7 runs, 100000000 loops each)

%timeit 3 if False else 8
18.1 ns ± 0.211 ns per loop (mean ± std. dev. of 7 runs, 100000000 loops each)

##----------------------------------------------------------------------------

%timeit 'if True:\n    3\nelse:\n    8'
8.67 ns ± 0.314 ns per loop (mean ± std. dev. of 7 runs, 100000000 loops each)

%timeit 'if False:\n    3\nelse:\n    8'
8.4 ns ± 0.0598 ns per loop (mean ± std. dev. of 7 runs, 100000000 loops each)

##----------------------------------------------------------------------------

##The last 2 are with quoting the statement.
%timeit '3 if True else 8'
8.73 ns ± 0.256 ns per loop (mean ± std. dev. of 7 runs, 100000000 loops each)

%timeit '3 if False else 8'
9.37 ns ± 0.215 ns per loop (mean ± std. dev. of 7 runs, 100000000 loops each)

I think the numbers speak for the statements. A shame really, cuz I love the ternary op.

However, the ternary op's still absolutely useful, especially in the cases where covering all the possibilities in function call params would create a massive repeating of code, which I absolutely hate.

Ternary Operator Vs If Else – Yawin Tutor, Difference between Ternary Operator and If Else. Ternary Operator is a programming statement. “If-Else” is a programming block. The statement is, of course, faster� The ternary operator is a substitute for an if-else statement. The ternary operator shortens the if-else statement into a single line. For example: Flutter vs Native vs React Native: Deep

Compare speeds of conditional operators and if-else statementsC , Compare the speeds of the conditional operator (ternary operator ? (Note that it's a good thing that the performance of the two statements is� A ternary operator takes three arguments. The first one (1st) is the condition, the second one (2nd) is executed if the condition is true, and the third one (3rd) is executed if the condition is

Program It: If/Else Statement vs. Ternary Operator, of which one is faster, the ternary operator or if/else statement, was asked again and again. We also capture the baseline performance. The conditional operator (also called the ternary operator) looks confusing enough that some programmers assume it must be more efficient than a comparable but longer if-else statement. This example uses the following code to compare the speeds of the conditional operator and an if-else statement.

Benefits of using the conditional ?: (ternary) operator, Prettiness of ternary operator vs. if statement, Performance. If / Else Statements vs Ternary Operators in JavaScript, The speed difference will be negligible� An if/else statement emphasises the branching first and what's to be done is secondary, while a ternary operator emphasises what's to be done over the selection of the values to do it with. In different situations, either may better reflect the programmer's "natural" perspective on the code and make it easier to understand, verify and maintain.

Comments
  • Just use whichever you feel makes the code more readable. If you're ever in a hot loop where it really may make a difference, code it both ways and measure the performance in the context of your actual code. There are likely to be other factors that are more important, such as the algorithm you use.
  • I think that may have more to do with timeit attempting to parse the triple quoted comment. I defined functions to evaluate that condition with an if-else statement and a ternary operator, used timeit.repeat for both with 100 repetitions, and got an average (for the default 1,000,000 run-throughs) of 0.81 seconds for the ternary operator, 0.88 seconds for the if-else statement.