Removed code relevant to versions below 3.6

.github/workflows/tests.yml

@@ -6,7 +6,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8, 3.9.0-rc - 3.9, pypy3]
+        python-version: [3.6, 3.7, 3.8, 3.9.0-rc - 3.9, pypy3]
 
     steps:
       - uses: actions/checkout@v2

lark/lexer.py

@@ -3,7 +3,7 @@
 import re
 from contextlib import suppress
 
-from .utils import classify, get_regexp_width, Py36, Serialize
+from .utils import classify, get_regexp_width, Serialize
 from .exceptions import UnexpectedCharacters, LexError, UnexpectedToken
 
 ###{standalone
@@ -38,19 +38,10 @@ class Pattern(Serialize):
     def max_width(self):
         raise NotImplementedError()
 
-    if Py36:
-        # Python 3.6 changed syntax for flags in regular expression
-        def _get_flags(self, value):
-            for f in self.flags:
-                value = ('(?%s:%s)' % (f, value))
-            return value
-
-    else:
-        def _get_flags(self, value):
-            for f in self.flags:
-                value = ('(?%s)' % f) + value
-            return value
-
+    def _get_flags(self, value):
+        for f in self.flags:
+            value = ('(?%s:%s)' % (f, value))
+        return value
 
 
 class PatternStr(Pattern):

lark/load_grammar.py

@@ -9,7 +9,7 @@ from ast import literal_eval
 from numbers import Integral
 from contextlib import suppress
 
-from .utils import bfs, Py36, logger, classify_bool, is_id_continue, is_id_start, bfs_all_unique
+from .utils import bfs, logger, classify_bool, is_id_continue, is_id_start, bfs_all_unique
 from .lexer import Token, TerminalDef, PatternStr, PatternRE
 
 from .parse_tree_builder import ParseTreeBuilder
@@ -475,18 +475,7 @@ class PrepareLiterals(Transformer_InPlace):
 
 
 def _make_joined_pattern(regexp, flags_set):
-    # In Python 3.6, a new syntax for flags was introduced, that allows us to restrict the scope
-    # of flags to a specific regexp group. We are already using it in `lexer.Pattern._get_flags`
-    # However, for prior Python versions, we still need to use global flags, so we have to make sure
-    # that there are no flag collisions when we merge several terminals.
-    flags = ()
-    if not Py36:
-        if len(flags_set) > 1:
-            raise GrammarError("Lark doesn't support joining terminals with conflicting flags in python <3.6!")
-        elif len(flags_set) == 1:
-            flags ,= flags_set
-
-    return PatternRE(regexp, flags)
+    return PatternRE(regexp, ())
 
 
 class TerminalTreeToPattern(Transformer):

lark/utils.py

@@ -13,8 +13,6 @@ logger.addHandler(logging.StreamHandler())
 logger.setLevel(logging.CRITICAL)
 
 
-Py36 = (sys.version_info[:2] >= (3, 6))
-
 NO_VALUE = object()
 
 

tests/test_parser.py

@@ -8,7 +8,7 @@ import os
 import sys
 from copy import copy, deepcopy
 
-from lark.utils import Py36, isascii
+from lark.utils import isascii
 
 from lark import Token, Transformer_NonRecursive, LexError
 
@@ -1545,7 +1545,6 @@ def _make_parser_test(LEXER, PARSER):
             self.assertEqual( g.parse('"hello"').children, ['"hello"'])
             self.assertEqual( g.parse("'hello'").children, ["'hello'"])
 
-        @unittest.skipIf(not Py36, "Required re syntax only exists in python3.6+")
         def test_join_regex_flags(self):
             g = r"""
                 start: A

tox.ini

@@ -1,16 +1,12 @@
 [tox]
-envlist = py27, py34, py35, py36, py37, py38, py39, pypy, pypy3
+envlist = py36, py37, py38, py39, pypy, pypy3
 skip_missing_interpreters=true
 
 [travis]
-2.7 = py27
-3.4 = py34
-3.5 = py35
 3.6 = py36
 3.7 = py37
 3.8 = py38
 3.9 = py39
-pypy = pypy
 pypy3 = pypy3
 
 [testenv]