text: #!/usr/bin/env python
  
  # Copyright (c) 2018, Michael Boyle
  # See LICENSE file for details: <https://github.com/moble/quaternion/blob/master/LICENSE>
  
  # Construct the version number from the date and time this python version was created.
  from os import environ
  from sys import platform
  on_windows = ('win' in platform.lower() and not 'darwin' in platform.lower())
  if "package_version" in environ:
      version = environ["package_version"]
      print("Setup.py using environment version='{0}'".format(version))
  else:
      print("The variable 'package_version' was not present in the environment")
      try:
          # For cases where this is being installed from git.  This gives the true version number.
          from subprocess import check_output
          if on_windows:
              version = check_output("""git log -1 --format=%cd --date=format:'%Y.%m.%d.%H.%M.%S'""", shell=False)
              version = version.decode('ascii').strip().replace('.0', '.').replace("'", "")
          else:
              try:
                  from subprocess import DEVNULL as devnull
                  version = check_output("""git log -1 --format=%cd --date=format:'%Y.%-m.%-d.%-H.%-M.%-S'""", shell=True, stderr=devnull)
              except AttributeError:
                  from os import devnull
                  version = check_output("""git log -1 --format=%cd --date=format:'%Y.%-m.%-d.%-H.%-M.%-S'""", shell=True, stderr=devnull)
              version = version.decode('ascii').rstrip()
          print("Setup.py using git log version='{0}'".format(version))
      except Exception:
          # For cases where this isn't being installed from git.  This gives the wrong version number,
          # but at least it provides some information.
          #import traceback
          #print(traceback.format_exc())
          try:
              from time import strftime, gmtime
              try:
                  version = strftime("%Y.%-m.%-d.%-H.%-M.%-S", gmtime())
              except ValueError:  # because Windows
                  version = strftime("%Y.%m.%d.%H.%M.%S", gmtime()).replace('.0', '.')
              print("Setup.py using strftime version='{0}'".format(version))
          except:
              version = '0.0.0'
              print("Setup.py failed to determine the version; using '{0}'".format(version))
  with open('_version.py', 'w') as f:
      f.write('__version__ = "{0}"'.format(version))
  
  
  long_description = """\
  This package creates a quaternion type in python, and further enables numpy to create and manipulate arrays of
  quaternions.  The usual algebraic operations (addition and multiplication) are available, along with numerous
  properties like norm and various types of distance measures between two quaternions.  There are also
  additional functions like "squad" and "slerp" interpolation, and conversions to and from axis-angle, matrix,
  and Euler-angle representations of rotations.  The core of the code is written in C for speed.
  """
  
  
  if __name__ == "__main__":
      import numpy
      from setuptools import setup, Extension
      # from distutils.core import setup, Extension
      from distutils.errors import DistutilsError
      if numpy.__dict__.get('quaternion') is not None:
          raise DistutilsError('The target NumPy already has a quaternion type')
      extension = Extension(
          name='quaternion.numpy_quaternion',  # This is the name of the object file that will be compiled
          sources=['quaternion.c', 'numpy_quaternion.c'],
          extra_compile_args=['/O2' if on_windows else '-O3'],
          depends=['quaternion.c', 'quaternion.h', 'numpy_quaternion.c'],
          include_dirs=[numpy.get_include()]
      )
      setup(name='numpy-quaternion',  # Uploaded to pypi under this name
            packages=['quaternion'],  # This is the actual package name
            package_dir={'quaternion': ''},
            ext_modules=[extension],
            version=version,
            install_requires=[
                'numpy>=1.13',
            ],
            url='https://github.com/moble/quaternion',
            author='Michael Boyle',
            author_email='mob22@cornell.edu',
            description='Add built-in support for quaternions to numpy',
            long_description=long_description,
      )
  