1. typing.NamedTuple

• added in Python 3.5 and apply type hints 3.6
• nicer syntax, inheritance, type annotations, default values(3.6.1), equally fast
• example

from typing import NamedTupleclass Student(NamedTuple):name: straddress: strage: intsex: str>>> tommy = Student(name='Tommy Johnson', address='Main street', age=22, sex='M')>>> tommyStudent(name='Tommy Johnson', address='Main street', age=22, sex='M')

The NamedTuple class is a subclass of tuple.

>>> isinstance(tommy, tuple)True>>> tommy[0]'Tommy Johnson'

using default values

class MaleStudent(Student):sex: str = 'M'  # default value, requires Python >= 3.6.1>>> MaleStudent(name='Tommy Johnson', address='Main street', age=22)MaleStudent(name='Tommy Johnson', address='Main street', age=22, sex='M')  # note that sex defaults to 'M'

2. typing.Optional

• added in Python 3.6

• Optional Type

• Optional[X] is equivalent to Union[X, None].

  • Union: Union type; Union[X, Y] means either X or Y.
  • example

  Union[Union[int, str], float] == Union[int, str, float]Union[int] == int  # The constructor actually returns intUnion[int, str, int] == Union[int, str]Union[int, str] == Union[str, int]Union[int, object] == object
  

3. types.MappingProxyType

• added in Python 3.3
• be used as a read-only dict
• example

>>> from  types import MappingProxyType>>> data = {'a': 1, 'b':2}>>> read_only = MappingProxyType(data)>>> del read_only['a']TypeError: 'mappingproxy' object does not support item deletion>>> read_only['a'] = 3TypeError: 'mappingproxy' object does not support item assignment

• it helps us avoid a whole class of difficult-to-find bugs.
• Note though that while read_only is read-only, it is not immutable, so if you change data, read_only will change too: