bpo-37163: Deprecate passing argument obj of dataclasses.replace() by keyword. (GH-13877)
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index b035cbb..1871372 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -1206,7 +1206,7 @@
unsafe_hash=unsafe_hash, frozen=frozen)
-def replace(obj, **changes):
+def replace(*args, **changes):
"""Return a new object replacing specified fields with new values.
This is especially useful for frozen classes. Example usage:
@@ -1220,6 +1220,17 @@
c1 = replace(c, x=3)
assert c1.x == 3 and c1.y == 2
"""
+ if len(args) > 1:
+ raise TypeError(f'replace() takes 1 positional argument but {len(args)} were given')
+ if args:
+ obj, = args
+ elif 'obj' in changes:
+ obj = changes.pop('obj')
+ import warnings
+ warnings.warn("Passing 'obj' as keyword argument is deprecated",
+ DeprecationWarning, stacklevel=2)
+ else:
+ raise TypeError("replace() missing 1 required positional argument: 'obj'")
# We're going to mutate 'changes', but that's okay because it's a
# new dict, even if called with 'replace(obj, **my_changes)'.
@@ -1255,3 +1266,4 @@
# changes that aren't fields, this will correctly raise a
# TypeError.
return obj.__class__(**changes)
+replace.__text_signature__ = '(obj, /, **kwargs)'