Provide an easy way to check BLAS/LAPACK linkage from python

According to the answers to this stackoverflow question the only way to check if Numpy is using the system BLAS/LAPACK is to inspect the output of ldd on some library belonging to numpy hidden deep in the filesystem. In fact I am not 100 % sure that I interprete my results correctly.

It would be nice with something like

>>>print(numpy._lapack_version_)
3.4.2

>>>print(numpy._blas_version_)
OpenBLAS 0.2.8

or if we are using the fallback

>>>print(numpy._lapack_version_)
fallback

[charris]

You can get some information from np.__config__.

In [5]: np.__config__.show()
atlas_threads_info:
    libraries = ['lapack', 'ptf77blas', 'ptcblas', 'atlas']
    library_dirs = ['/usr/lib64/atlas']
    define_macros = [('ATLAS_INFO', '"\\"3.8.4\\""')]
    language = f77
    include_dirs = ['/usr/include']
blas_opt_info:
    libraries = ['ptf77blas', 'ptcblas', 'atlas']
    library_dirs = ['/usr/lib64/atlas']
    define_macros = [('ATLAS_INFO', '"\\"3.8.4\\""')]
    language = c
    include_dirs = ['/usr/include']
atlas_blas_threads_info:
    libraries = ['ptf77blas', 'ptcblas', 'atlas']
    library_dirs = ['/usr/lib64/atlas']
    define_macros = [('ATLAS_INFO', '"\\"3.8.4\\""')]
    language = c
    include_dirs = ['/usr/include']
openblas_info:
  NOT AVAILABLE
lapack_opt_info:
    libraries = ['lapack', 'ptf77blas', 'ptcblas', 'atlas']
    library_dirs = ['/usr/lib64/atlas']
    define_macros = [('ATLAS_INFO', '"\\"3.8.4\\""')]
    language = f77
    include_dirs = ['/usr/include']
lapack_mkl_info:
  NOT AVAILABLE
blas_mkl_info:
  NOT AVAILABLE
mkl_info:
  NOT AVAILABLE

[dhimmel]

numpy.show_config() provides the same results as numpy.__config__.show(), but perhaps is a more intended use of the numpy API.