pythongh-118465: Optimize inspect.findsource() for classes

Lib/inspect.py

@@ -1038,25 +1038,40 @@ class ClassFoundException(Exception):
 class _ClassFinder(ast.NodeVisitor):
 
  def __init__(self, cls, tree, lines, qualname):
- self.stack = []
+ self.names = qualname.split('.')
+ self.pos = 0
  self.cls = cls
  self.tree = tree
  self.lines = lines
- self.qualname = qualname
  self.lineno_found = []
 
+ def generic_visit(self, node):
+ if isinstance(node, ast.stmt):
+ super().generic_visit(node)
+
+ visit_Module = ast.NodeVisitor.generic_visit
+
+ # For optimization. Skip the most common stmt nodes that cannot
+ # contain sub-statements.
+ def visit_Expr(self, node): pass
+ def visit_Assign(self, node): pass
+ def visit_Return(self, node): pass
+
  def visit_FunctionDef(self, node):
- self.stack.append(node.name)
- self.stack.append('<locals>')
+ if (len(self.names) < self.pos + 3 or
+ node.name != self.names[self.pos] or
+ '<locals>' != self.names[self.pos+1]):
+ return
+ self.pos += 2
  self.generic_visit(node)
- self.stack.pop()
- self.stack.pop()
+ self.pos -= 2
 
  visit_AsyncFunctionDef = visit_FunctionDef
 
  def visit_ClassDef(self, node):
- self.stack.append(node.name)
- if self.qualname == '.'.join(self.stack):
+ if node.name != self.names[self.pos]:
+ return
+ if len(self.names) == self.pos + 1:
  # Return the decorator for the class if present
  if node.decorator_list:
  line_number = node.decorator_list[0].lineno
@@ -1065,8 +1080,10 @@ def visit_ClassDef(self, node):
 
  # decrement by one since lines starts with indexing by zero
  self.lineno_found.append((line_number - 1, node.end_lineno))
+ return
+ self.pos += 1
  self.generic_visit(node)
- self.stack.pop()
+ self.pos -= 1
 
  def get_lineno(self):
  self.visit(self.tree)

Misc/NEWS.d/next/Library/2024-05-01-14-53-54.gh-issue-118465.1wxT3U.rst

@@ -0,0 +1 @@
+Optimize :func:`inspect.findsource` for classes.