You need to specify where to find Python:
RegisterExternalEvaluator[
"Python",
"C:\\bin\\Anaconda3\\python.EXE"]
Register a Python-Numpy library:
RegisterExternalEvaluator[
"Python-NumPy",
"C:\\bin\\Anaconda3\\python.EXE"]
How to import a Numpy library
ExternalEvaluate[
"Python",
"import numpy; x = numpy.pi; x**2"
]
Import any libraries:
ExternalEvaluate[
"Python",
"from sympy import isprime; isprime(7)"
]
Examples from the following websites: https://www.johndcook.com/blog/2019/04/18/calling-python-from-mathematica/.