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I get a SyntaxError: invalid syntax error when I try the new typed namedtuple syntax:
class Employee(NamedTuple):
name: str
id: int
in Python 3.5.2 even though according to the documentation it should be valid from 3.5+ onwards. Am I missing something? I've imported NamedTuple from typing in the code.
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Python's namedtuple() is a factory function available in collections . It allows you to create tuple subclasses with named fields. You can access the values in a given named tuple using the dot notation and the field names, like in obj. attr .
The namedtuple is a function that returns a new named tuple class. In other words, the namedtuple() is a class factory. The namedtuple function accepts the following arguments to generate a class: A class name that specifies the name of the named tuple class.
Since a named tuple is a tuple, and tuples are immutable, it is impossible to change the value of a field. In this case, we have to use another private method _replace() to replace values of the field. The _replace() method will return a new named tuple.
Named Tuple Python's tuple is a simple data structure for grouping objects with different types. Its defining feature is being immutable. An immutable object is an object whose state cannot be modified after it is created.
The syntax to declare the types for the name and id fields you are using requires Python 3.6 or up. Python 3.5 does not support the variable-level type hints required.
From the typing.NamedTuple documentation:
Changed in version 3.6: Added support for PEP 526 variable annotation syntax.
Use the backwards compatible syntax also included in the documentation:
Employee = NamedTuple('Employee', [('name', str), ('id', int)])
so listing the field names as (name, type) tuples.
If you are using Python 3.5, you may want to switch to the Python 3.5 version of the documentation instead (there is a selector in the top-left corner, or you can just replace the 3 in the URL with 3.5).
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