Issue #19137: The pprint module now correctly formats empty set and frozenset

and instances of set and frozenset subclasses.

Lib/pprint.py

@@ -185,25 +185,18 @@ class PrettyPrinter:
             if issubclass(typ, list):
                 write('[')
                 endchar = ']'
-            elif issubclass(typ, set):
-                if not length:
-                    write('set()')
-                    return
-                write('set([')
-                endchar = '])'
-                object = _sorted(object)
-                indent += 4
-            elif issubclass(typ, frozenset):
+            elif issubclass(typ, tuple):
+                write('(')
+                endchar = ')'
+            else:
                 if not length:
-                    write('frozenset()')
+                    write(rep)
                     return
-                write('frozenset([')
+                write(typ.__name__)
+                write('([')
                 endchar = '])'
+                indent += len(typ.__name__) + 1
                 object = _sorted(object)
-                indent += 10
-            else:
-                write('(')
-                endchar = ')'
             if self._indent_per_level > 1 and sepLines:
                 write((self._indent_per_level - 1) * ' ')
             if length:

Misc/NEWS

@@ -32,6 +32,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #19137: The pprint module now correctly formats empty set and frozenset
+  and instances of set and frozenset subclasses.
+
 - Issue #16040: CVE-2013-1752: nntplib: Limit maximum line lengths to 2048 to
   prevent readline() calls from consuming too much memory.  Patch by Jyrki
   Pulliainen.