Fix for Python 3.7

lark/tools/standalone.py

@@ -46,8 +46,8 @@ from lark.parsers.lalr_analysis import Shift, Reduce
 
 from ..grammar import Rule
 
-__dir__ = path.dirname(__file__)
-__larkdir__ = path.join(__dir__, path.pardir)
+_dir = path.dirname(__file__)
+_larkdir = path.join(_dir, path.pardir)
 
 
 EXTRACT_STANDALONE_FILES = [
@@ -177,10 +177,10 @@ def main(fobj, start):
     print('# The file was automatically generated by Lark v%s' % lark.__version__)
 
     for pyfile in EXTRACT_STANDALONE_FILES:
-        with open(os.path.join(__larkdir__, pyfile)) as f:
+        with open(os.path.join(_larkdir, pyfile)) as f:
             print (extract_sections(f)['standalone'])
 
-    with open(os.path.join(__larkdir__, 'grammar.py')) as grammar_py:
+    with open(os.path.join(_larkdir, 'grammar.py')) as grammar_py:
         print(grammar_py.read())
 
     print('Shift = 0')