PERF: Eliminate slow check for pypy during numpy import (numpy#22163)

This PR replaces the import of platform and a call to platform.python_implementation() with a check using sys.implementation.name to improve the numpy import time. The improvement is about 5-10 ms (system dependent).

Also see numpy#22061

Co-authored-by: Matti Picus <[email protected]>

Author: eendebakpt

numpy/core/_internal.py

@@ -7,7 +7,6 @@
 import ast
 import re
 import sys
-import platform
 import warnings
 
 from .multiarray import dtype, array, ndarray, promote_types
@@ -16,7 +15,7 @@
 except ImportError:
     ctypes = None
 
-IS_PYPY = platform.python_implementation() == 'PyPy'
+IS_PYPY = sys.implementation.name == 'pypy'
 
 if sys.byteorder == 'little':
     _nbo = '<'

numpy/testing/_private/utils.py

@@ -48,7 +48,7 @@ class KnownFailureException(Exception):
 KnownFailureTest = KnownFailureException  # backwards compat
 verbose = 0
 
-IS_PYPY = platform.python_implementation() == 'PyPy'
+IS_PYPY = sys.implementation.name == 'pypy'
 IS_PYSTON = hasattr(sys, "pyston_version_info")
 HAS_REFCOUNT = getattr(sys, 'getrefcount', None) is not None and not IS_PYSTON
 HAS_LAPACK64 = numpy.linalg.lapack_lite._ilp64