allow restricting the output to certain interesting lines in PrintTree()

Cython/Compiler/Visitor.py

@@ -709,12 +709,17 @@ class PrintTree(TreeVisitor):
     """Prints a representation of the tree to standard output.
     Subclass and override repr_of to provide more information
     about nodes. """
-    def __init__(self):
+    def __init__(self, start=None, end=None):
         TreeVisitor.__init__(self)
         self._indent = ""
+        if start is not None or end is not None:
+            self._line_range = (start or 0, end or 2**30)
+        else:
+            self._line_range = None
 
     def indent(self):
         self._indent += "  "
+
     def unindent(self):
         self._indent = self._indent[:-2]
 
@@ -728,6 +733,8 @@ class PrintTree(TreeVisitor):
     # under the parent-node, not displaying the list itself in
     # the hierarchy.
     def visit_Node(self, node):
+        line = node.pos[1]
+        if self._line_range is None or self._line_range[0] <= line <= self._line_range[1]:
             if len(self.access_path) == 0:
                 name = "(root)"
             else: