Introduction
On October 5, Python released a new version 3.9.0. In this article, we have given the information about the new release highlights, new features, new models, with some source to try it in your own environment.
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1. Dictionary Merge & Update Operators
Merge/union (|) and update/in-place union (|=) operators have been added to the built-in dict class. Those complement the existing dict.update and {**d1, **d2} methods of merging dictionaries.
Example
>>> x = {"key1": "value1 from x", "key2": "value2 from x"}
>>> y = {"key2": "value2 from y", "key3": "value3 from y"}
Merge
The | operator is used for calculating the union of sets
Example:
>>> x | y
{'key1': 'value1 from x', 'key2': 'value2 from y', 'key3': 'value3 from y'}
>>> y | x
{'key2': 'value2 from x', 'key3': 'value3 from y', 'key1': 'value1 from x'}
Update
The basic use of |= is to update a dictionary in place, similar to .update()
Example:
>>> x |= y
>>> x
{'key1': 'value1 from x', 'key2': 'value2 from y', 'key3': 'value3 from y'}
2. New String Methods to Remove Prefixes and Suffixes
Example
>>> sentence = 'New String Methods to Remove Prefixes and Suffixes in python'
>>> sentence.removesuffix('python')
'New String Methods to Remove Prefixes and Suffixes in '
>>> sentence.removeprefix("New")
' String Methods to Remove Prefixes and Suffixes in python'
3. Type Hinting Generics in Standard Collections
In type annotations you can now use built-in collection types such as list and dict as generic types instead of importing the corresponding capitalized types (e.g. List or Dict) from typing. Some other types in the standard library are also now generic, for example queue.Queue.
Example:
def greet_all(names: list[str]) -> None:
for name in names:
print("Hello", name)
4. New Modules
a. Zoneinfo
The zoneinfo module brings support for the IANA time zone database to the standard library. It adds zoneinfo.ZoneInfo, a concrete datetime.tzinfo implementation backed by the system’s time zone data
Example:
>>> from zoneinfo import ZoneInfo
>>> from datetime import datetime, timedelta
>>> dt = datetime(2020, 11, 19, tzinfo=ZoneInfo("Asia/Kolkata"))
>>> print(dt)
2020-11-19 00:00:00+05:30
>>> dt.tzname()
'IST'
b. graphlib
A new module, graphlib, was added that contains the graphlib.TopologicalSorter class to offer functionality to perform topological sorting of graphs.
Example:
>>> from graphlib import TopologicalSorter
>>> graph = {"D": {"B", "C"}, "C": {"A"}, "B": {"A"}}
>>> ts = TopologicalSorter(graph)
>>> tuple(ts.static_order())
('A', 'C', 'B', 'D')
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