https://hg.python.org/cpython/rev/b33c3f26eefa changeset: 106327:b33c3f26eefa branch: 3.6 parent: 106323:ff3312ce1d14 user: Raymond Hettinger <python@rcn.com> date: Sat Jan 28 20:16:40 2017 -0800 summary: Issue 29310: Document typing.NamedTuple default argument syntax files: Doc/library/typing.rst | 22 ++++++++++++++++++---- 1 files changed, 18 insertions(+), 4 deletions(-) diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst --- a/Doc/library/typing.rst +++ b/Doc/library/typing.rst @@ -735,10 +735,21 @@ Employee = collections.namedtuple('Employee', ['name', 'id']) - The resulting class has one extra attribute: ``_field_types``, - giving a dict mapping field names to types. (The field names - are in the ``_fields`` attribute, which is part of the namedtuple - API.) + To give a field a default value, you can assign to it in the class body:: + + class Employee(NamedTuple): + name: str + id: int = 3 + + employee = Employee('Guido') + assert employee.id == 3 + + Fields with a default value must come after any fields without a default. + + The resulting class has two extra attributes: ``_field_types``, + giving a dict mapping field names to types, and ``field_defaults``, a dict + mapping field names to default values. (The field names are in the + ``_fields`` attribute, which is part of the namedtuple API.) Backward-compatible usage:: @@ -747,6 +758,9 @@ .. versionchanged:: 3.6 Added support for :pep:`526` variable annotation syntax. + .. versionchanged:: 3.6.1 + Added support for default values. + .. function:: NewType(typ) A helper function to indicate a distinct types to a typechecker, -- Repository URL: https://hg.python.org/cpython