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Fixed #29049 -- Added slicing notation to F expressions.

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Co-authored-by: Priyansh Saxena <askpriyansh@gmail.com>
Co-authored-by: Niclas Olofsson <n@niclasolofsson.se>
Co-authored-by: David Smith <smithdc@gmail.com>
Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Co-authored-by: Abhinav Yadav <abhinav.sny.2002@gmail.com>
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Nick Pope 2023-12-30 07:24:30 +00:00 • committed by GitHub
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docs/ref/models/expressions.txt
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@ -183,6 +183,28 @@ the field value of each one, and saving each one back to the database::
* getting the database, rather than Python, to do work
* reducing the number of queries some operations require
.. _slicing-using-f:
Slicing ``F()`` expressions
~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. versionadded:: 5.1
For string-based fields, text-based fields, and
:class:`~django.contrib.postgres.fields.ArrayField`, you can use Python's
array-slicing syntax. The indices are 0-based and the ``step`` argument to
``slice`` is not supported. For example:
.. code-block:: pycon
>>> # Replacing a name with a substring of itself.
>>> writer = Writers.objects.get(name="Priyansh")
>>> writer.name = F("name")[1:5]
>>> writer.save()
>>> writer.refresh_from_db()
>>> writer.name
'riya'
.. _avoiding-race-conditions-using-f:
Avoiding race conditions using ``F()``