Exponentiation in Python - should I prefer operator instead of math pow and math sqrt

Question

In my field it s very common to square some numbers  operate them together  and take the square root of the result  This is done in pythagorean theorem  and the RMS calculation  for example   In numpy  I have done the following   result   numpy sqrt numpy sum numpy pow some vector  2      And in pure python something like this would be expected   result   math sqrt math pow A  2    math pow B 2     example with two dimensions    However  I have been using this pure python form  since I find it much more compact  import-independent  and seemingly equivalent   result    A  2   B  2   0 5     two dimensions result    A  2   B  2   C  2   D  2   0 5   I have heard some people argue that the    operator is sort of a hack  and that squaring a number by exponentiating it by 0 5 is not so readable  But what I d like to ask is if    Is there any COMPUTATIONAL reason to prefer the former two alternatives over the third one s     Thanks for reading

User · Answer

Even in base Python you can do the computation in generic form

result = sum(x**2 for x in some_vector) ** 0.5

x ** 2 is surely not an hack and the computation performed is the same (I checked with cpython source code). I actually find it more readable (and readability counts).

Using instead x ** 0.5 to take the square root doesn't do the exact same computations as math.sqrt as the former (probably) is computed using logarithms and the latter (probably) using the specific numeric instruction of the math processor.

I often use x ** 0.5 simply because I don't want to add math just for that. I'd expect however a specific instruction for the square root to work better (more accurately) than a multi-step operation with logarithms.

User · Answer

math sqrt is the C implementation of square root and is therefore different from using the    operator which implements Python s built-in pow function  Thus  using math sqrt actually gives a different answer than using the    operator and there is indeed a computational reason to prefer numpy or math module implementation over the built-in  Specifically the sqrt functions are probably implemented in the most efficient way possible whereas    operates over a large number of bases and exponents and is probably unoptimized for the specific case of square root  On the other hand  the built-in pow function handles a few extra cases like  complex numbers  unbounded integer powers  and modular exponentiation    See this Stack Overflow question for more information on the difference  between    and math sqrt   In terms of which is more  Pythonic   I think we need to discuss the very definition of that word  From the official Python glossary  it states that a piece of code or idea is Pythonic if it  closely follows the most common idioms of the Python language  rather than implementing code using concepts common to other languages   In every single other language I can think of  there is some math module with basic square root functions  However there are languages that lack a power operator like    e g  C    So    is probably more Pythonic  but whether or not it s objectively better depends on the use case

[python] Exponentiation in Python - should I prefer ** operator instead of math.pow and math.sqrt?

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