What's new in Python 3.9

2020-11-10T00:00:00+00:00

Python 3.9</h2>
Python 3.9 has been released on October 5, 2020.</p>

Add Union Operators To dict (PEP 584)</h2>

This allows the union operation to be performed on dicts:</p>

>>></span> a</span> =</span> {</span>'x'</span>:</span> 1</span>,</span> 'y'</span>:</span> 2</span>,</span> 'z'</span>:</span> 3</span>}</span></span>
>>></span> e</span> =</span> {</span>'w'</span>:</span> 'hello world'</span>}</span></span>
>>></span> a</span> |</span> e</span></span>
{</span>'x'</span>:</span> 1</span>,</span> 'y'</span>:</span> 2</span>,</span> 'z'</span>:</span> 3</span>,</span> 'w'</span>:</span> 'hello world'</span>}</span></span></code></pre>
And also:</p>
>>></span> x</span> =</span> a</span></span>
>>></span> x</span></span>
{</span>'x'</span>:</span> 1</span>,</span> 'y'</span>:</span> 2</span>,</span> 'z'</span>:</span> 3</span>}</span></span>
>>></span> x</span> |=</span> e</span></span>
>>></span> x</span></span>
{</span>'x'</span>:</span> 1</span>,</span> 'y'</span>:</span> 2</span>,</span> 'z'</span>:</span> 3</span>,</span> 'w'</span>:</span> 'hello world'</span>}</span></span></code></pre>Type Hinting Generics In Standard Collections (PEP 585)</h2>
This feature enables type hinting using the standard collections without having to rely on the typings</code> module.</p>
Previously to type hint a list you would do:</p>
from</span> typings</span> import</span> List</span></span>
</span>
def</span> somefunc</span>(</span>a</span>:</span> List[</span>int</span>]):</span></span>
    pass</span></span></code></pre>
Now you can use the standard type:</p>
</span>
def</span> somefunc</span>(</span>a</span>:</span> list[</span>int</span>]):</span></span>
    pass</span></span></code></pre>
From this version, importing collections</strong> from typings</code> is deprecated, and they will be removed in 5 years.</p>
Flexible function and variable annotations (PEP 593)</h2>
This feature adds a new type Annotated</code> which allows us to extend type annotations with metadata.</p>
This allows a type T</code> to be annotated with metadata x</code> like so:</p>
T1</span> =</span> Annotated[T</span>,</span> x]</span></span>
</span>
# E.g</span></span>
UnsignedShort</span> =</span> Annotated[</span>int</span>,</span> struct2</span>.</span>ctype</span>(</span>'H'</span>)]</span></span>
SignedChar</span> =</span> Annotated[</span>int</span>,</span> struct2</span>.</span>ctype</span>(</span>'b'</span>)]</span></span>
</span>
# Multiple type annotations are supported</span></span>
T2</span> =</span> Annotated[</span>int</span>,</span> ValueRange</span>(</span>3</span>,</span> 10</span>)</span>,</span> ctype</span>(</span>"char"</span>)]</span></span></code></pre>
The metadata can then be used for static or runtime analysis with tools such as mypy</a></p>
This feature allows authors to introduce new data types with graceful degradation,
for example if mypy doesn't know how to parse X Annotation it should just ignore its metadata and use the annotated type.</p>
Relaxing Grammar Restrictions On Decorators (PEP 614)</h2>
Python currently requires that all decorators consist of a dotted name, optionally followed by a single call. This PEP proposes removing these limitations and allowing decorators to be any valid expression.</p>
An expression here means "anything that's valid as a test in if, elif, and while blocks".</p>
Basically this:</p>
button_0</span> =</span> buttons[</span>0</span>]</span></span>
</span>
@button_0</span>.</span>clicked</span>.</span>connect</span></span>
def</span> spam</span>():</span></span>
    pass</span></span></code></pre>
Can now be:</p>
@buttons</span>[0].clicked.connect</span></span>
def</span> spam</span>():</span></span>
    pass</span></span></code></pre>Support for the IANA Time Zone Database in the Standard Library</h2>
This feature adds a new module zoneinfo</code> that provides a concrte time zone implementation supporting the IANA time zone database.</p>
You can find more about this module here: zoneinfo</a></p>
Example:</p>
>>></span> from</span> zoneinfo</span> import</span> ZoneInfo</span></span>
>>></span> from</span> datetime</span> import</span> datetime</span>,</span> timedelta</span></span>
</span>
>>></span> dt</span> =</span> datetime</span>(</span>2020</span>,</span> 10</span>,</span> 31</span>,</span> 12</span>,</span> tzinfo</span>=</span>ZoneInfo</span>(</span>"America/Los_Angeles"</span>))</span></span>
>>></span> print</span>(dt)</span></span>
2020</span>-</span>10</span>-</span>31 12</span>:</span>00</span>:</span>00</span>-</span>0</span>7</span>:</span>00</span></span>
</span>
>>></span> dt</span>.</span>tzname</span>()</span></span>
'PDT'</span></span></code></pre>String methods to remove prefixes and suffixes</h2>
Adds two new methods, removeprefix()</a> and removesuffix()</a>, to the APIs of Python's various string objects.</p>

Edgar Luque - python

What's new in Python 3.9

Python 3.9</h2> Python 3.9 has been released on October 5, 2020.</p>

Support for the IANA Time Zone Database in the Standard Library</h2> This feature adds a new module zoneinfo</code> that provides a concrte time zone implementation supporting the IANA time zone database.</p>

String methods to remove prefixes and suffixes</h2> Adds two new methods, removeprefix()</a> and removesuffix()</a>, to the APIs of Python's various string objects.</p>

Python 3.9</h2>
Python 3.9 has been released on October 5, 2020.</p>

String methods to remove prefixes and suffixes</h2>
Adds two new methods, removeprefix()</a> and removesuffix()</a>, to the APIs of Python's various string objects.</p>