BUG: add py39 compat check for ast.slice pandas-dev#32766 (pandas-dev#36080)

Author: fangchenli

pandas/core/computation/expr.py

@@ -10,6 +10,8 @@
 
 import numpy as np
 
+from pandas.compat import PY39
+
 import pandas.core.common as com
 from pandas.core.computation.ops import (
     ARITH_OPS_SYMS,
@@ -186,7 +188,6 @@ def _filter_nodes(superclass, all_nodes=_all_nodes):
 _stmt_nodes = _filter_nodes(ast.stmt)
 _expr_nodes = _filter_nodes(ast.expr)
 _expr_context_nodes = _filter_nodes(ast.expr_context)
-_slice_nodes = _filter_nodes(ast.slice)
 _boolop_nodes = _filter_nodes(ast.boolop)
 _operator_nodes = _filter_nodes(ast.operator)
 _unary_op_nodes = _filter_nodes(ast.unaryop)
@@ -197,6 +198,9 @@ def _filter_nodes(superclass, all_nodes=_all_nodes):
 _keyword_nodes = _filter_nodes(ast.keyword)
 _alias_nodes = _filter_nodes(ast.alias)
 
+if not PY39:
+    _slice_nodes = _filter_nodes(ast.slice)
+
 
 # nodes that we don't support directly but are needed for parsing
 _hacked_nodes = frozenset(["Assign", "Module", "Expr"])