some refactoring

DHParser/scripts/dhparser_cythonize_stringview.py

+#!/usr/bin/env python3
+# build.py - support for building cython extensions with poetry
+
+
+import os
+import sys
+from setuptools import setup
+
+
+try:
+    from Cython.Build import cythonize
+    has_cython = True
+except ImportError:
+    has_cython = False
+    def cythonize(filename, **options):
+        return []
+
+
+cythonize_modules = [
+    'DHParser/stringview.py',
+    # 'DHParser/toolkit.py',
+    # 'DHParser/preprocess.py',
+    # 'DHParser/error.py',
+    # 'DHParser/syntaxtree.py',
+    # 'DHParser/log.py',
+    # 'DHParser/parse.py',
+    # 'DHParser/trace.py',
+    # 'DHParser/transform.py',
+    # 'DHParser/compile.py',
+    # 'DHParser/ebnf.py',
+]
+
+
+def build(setup_kwargs={}):
+    if has_cython:
+
+        # find path of DHParser-module
+        scriptdir = os.path.dirname(os.path.abspath(__file__))
+        i = scriptdir.find('DHParser')
+        k = len('DHParser-submodule') if scriptdir[i:].startswith('DHParser-submodule') \
+            else len('DHParser')
+        if i >= 0:
+            dhparserdir = scriptdir[:i + k]
+            if dhparserdir not in sys.path:
+                sys.path.append(dhparserdir)
+        else:
+            dhparserdir = ''
+
+        save_cwd = os.getcwd()
+        os.chdir(dhparserdir)
+
+        # delete stale c and object-files
+        for name in os.listdir(dhparserdir):
+            if name.endswith('.c') or name.endswith('.pyd') or name.endswith('.so'):
+                os.remove(name)
+
+        # build cyhton modules inplace
+        sys.argv.extend(['build_ext', '--inplace'])
+        setup(
+            name='DHParser',
+            ext_modules=cythonize(cythonize_modules, nthreads=0, annotate=False),
+            zip_safe=False,
+        )
+
+        os.chdir(save_cwd)
+
+    else:
+        print('DHParser.scripts.build_cython: Cannot build Cython modules, '
+              'because Cython has not installed!\nTry running: pip install cython')
+
+
+if __name__ == "__main__":
+    build()

DHParser/stringview.py

@@ -98,8 +98,8 @@ def fast_real_indices(begin: Optional[int],
     """Returns the tuple of real (i.e. positive) indices from the slice
     indices `begin`,  `end`, assuming a string of size `length`.
     """
-    # cbegin = 0 if begin is None else begin
-    cbegin = begin if begin else 0
+    cbegin = 0 if begin is None else begin
+    # cbegin = begin if begin else 0
     cend = length if end is None else end
     return pack_index(cbegin, length), pack_index(cend, length)