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| -rw-r--r-- | Doc/reference/expressions.rst | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst index 8036a49..18abce3 100644 --- a/Doc/reference/expressions.rst +++ b/Doc/reference/expressions.rst @@ -1650,9 +1650,26 @@ Assignment expressions .. productionlist:: assignment_expression: [`identifier` ":="] `expression` -.. TODO: BPO-39868 +An assignment expression (sometimes also called a "named expression" or +"walrus") assigns an :token:`expression` to an :token:`identifier`, while also +returning the value of the :token:`expression`. -See :pep:`572` for more details about assignment expressions. +One common use case is when handling matched regular expressions: + +.. code-block:: python + + if matching := pattern.search(data): + do_something(matching) + +Or, when processing a file stream in chunks: + +.. code-block:: python + + while chunk := file.read(9000): + process(chunk) + +.. versionadded:: 3.8 + See :pep:`572` for more details about assignment expressions. .. _if_expr: |