Add ast.Constant
Issue #26146: Add a new kind of AST node: ast.Constant. It can be used by
external AST optimizers, but the compiler does not emit directly such node.
An optimizer can replace the following AST nodes with ast.Constant:
* ast.NameConstant: None, False, True
* ast.Num: int, float, complex
* ast.Str: str
* ast.Bytes: bytes
* ast.Tuple if items are constants too: tuple
* frozenset
Update code to accept ast.Constant instead of ast.Num and/or ast.Str:
* compiler
* docstrings
* ast.literal_eval()
* Tools/parser/unparse.py
diff --git a/Lib/ast.py b/Lib/ast.py
index 0170472..156a1f2 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -35,6 +35,8 @@
return compile(source, filename, mode, PyCF_ONLY_AST)
+_NUM_TYPES = (int, float, complex)
+
def literal_eval(node_or_string):
"""
Safely evaluate an expression node or a string containing a Python
@@ -47,7 +49,9 @@
if isinstance(node_or_string, Expression):
node_or_string = node_or_string.body
def _convert(node):
- if isinstance(node, (Str, Bytes)):
+ if isinstance(node, Constant):
+ return node.value
+ elif isinstance(node, (Str, Bytes)):
return node.s
elif isinstance(node, Num):
return node.n
@@ -62,24 +66,21 @@
in zip(node.keys, node.values))
elif isinstance(node, NameConstant):
return node.value
- elif isinstance(node, UnaryOp) and \
- isinstance(node.op, (UAdd, USub)) and \
- isinstance(node.operand, (Num, UnaryOp, BinOp)):
+ elif isinstance(node, UnaryOp) and isinstance(node.op, (UAdd, USub)):
operand = _convert(node.operand)
- if isinstance(node.op, UAdd):
- return + operand
- else:
- return - operand
- elif isinstance(node, BinOp) and \
- isinstance(node.op, (Add, Sub)) and \
- isinstance(node.right, (Num, UnaryOp, BinOp)) and \
- isinstance(node.left, (Num, UnaryOp, BinOp)):
+ if isinstance(operand, _NUM_TYPES):
+ if isinstance(node.op, UAdd):
+ return + operand
+ else:
+ return - operand
+ elif isinstance(node, BinOp) and isinstance(node.op, (Add, Sub)):
left = _convert(node.left)
right = _convert(node.right)
- if isinstance(node.op, Add):
- return left + right
- else:
- return left - right
+ if isinstance(left, _NUM_TYPES) and isinstance(right, _NUM_TYPES):
+ if isinstance(node.op, Add):
+ return left + right
+ else:
+ return left - right
raise ValueError('malformed node or string: ' + repr(node))
return _convert(node_or_string)
@@ -196,12 +197,19 @@
"""
if not isinstance(node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)):
raise TypeError("%r can't have docstrings" % node.__class__.__name__)
- if node.body and isinstance(node.body[0], Expr) and \
- isinstance(node.body[0].value, Str):
- if clean:
- import inspect
- return inspect.cleandoc(node.body[0].value.s)
- return node.body[0].value.s
+ if not(node.body and isinstance(node.body[0], Expr)):
+ return
+ node = node.body[0].value
+ if isinstance(node, Str):
+ text = node.s
+ elif isinstance(node, Constant) and isinstance(node.value, str):
+ text = node.value
+ else:
+ return
+ if clean:
+ import inspect
+ text = inspect.cleandoc(text)
+ return text
def walk(node):