The Mathematica function `ExternalEvalute`

lets you call Python from Mathematica. However, there are a few wrinkles.

I first pasted in an example from the Mathematica documentation and it failed.

ExternalEvaluate[ "Python", {"def f(x): return x**2", "f(3)"} ]

It turns out you (may) have to tell Mathematica where to find Python. I ran the following, tried again, and the example worked.

RegisterExternalEvaluator[ "Python", "C:\\bin\\Anaconda3\\python.EXE" ]

You can also run Python with NumPy loaded using

ExternalEvaluate["Python-NumPy", … ]

except that didn’t work the first time either. You have to register a `Python-NumPy`

evaluator separately. So I ran

RegisterExternalEvaluator[ "Python-NumPy", "C:\\bin\\Anaconda3\\python.EXE" ]

and then tried again calling Python code using NumPy. But then there’s the question of how it imports NumPy. Does it simply run `import numpy`

, or maybe `from numpy import *`

, or maybe `import numpy as np`

? It turns out the first possibility is what happens. So to print `pi`

from NumPy, your code string needs to be `numpy.pi`

.

You don’t need to use `Python-NumPy`

if you just do your own importing. For example, this code returns π².

ExternalEvaluate[ "Python", "import numpy; x = numpy.pi; x**2" ]

And you can import any library you’d like, not just NumPy.

ExternalEvaluate[ "Python", "from sympy import isprime; isprime(7)" ]

Everything above applies to Mathematica 11.3 and Mathematica 12.