This is an automated email from the ASF dual-hosted git repository.
potiuk pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/airflow.git
The following commit(s) were added to refs/heads/main by this push:
new ca755fbcac0 Explain f-string conflicts with Jinja templating (#48712)
ca755fbcac0 is described below
commit ca755fbcac055bb8bcd567873282d0dce848adc7
Author: Kacper Kulczak <17738154+kkulc...@users.noreply.github.com>
AuthorDate: Tue Apr 8 16:31:25 2025 +0200
Explain f-string conflicts with Jinja templating (#48712)
* Explain f-string conflicts with Jinja templating
* Fixed spaces
* Update operators.rst. - removed traling spaces
* Update operators.rst
Doubled back ticks
---------
Co-authored-by: Kacper <>
---
airflow-core/docs/core-concepts/operators.rst | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/airflow-core/docs/core-concepts/operators.rst
b/airflow-core/docs/core-concepts/operators.rst
index 524a43e04a5..0d66ba3f61d 100644
--- a/airflow-core/docs/core-concepts/operators.rst
+++ b/airflow-core/docs/core-concepts/operators.rst
@@ -304,3 +304,30 @@ If you upgrade your environment and get the following
error:
AttributeError: 'str' object has no attribute '__module__'
change name from ``params`` in your operators.
+
+Templating Conflicts with f-strings
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+When constructing strings for templated fields (like ``bash_command`` in
``BashOperator``) using Python f-strings, be mindful of the interaction between
f-string interpolation and Jinja templating syntax. Both use curly braces
(``{}``).
+
+Python f-strings interpret double curly braces (``{{`` and ``}}``) as escape
sequences for literal single braces (``{`` and ``}``). However, Jinja uses
double curly braces (``{{ variable }}``) to denote variables for templating.
+
+If you need to include a Jinja template expression (e.g., ``{{ ds }}``)
literally within a string defined using an f-string, so that Airflow's Jinja
engine can process it later, you must escape the braces for the f-string by
doubling them *again*. This means using **four** curly braces:
+
+.. code-block:: python
+
+ t1 = BashOperator(
+ task_id="fstring_templating_correct",
+ bash_command=f"echo Data interval start: {{{{ ds }}}}",
+ dag=dag,
+ )
+
+ python_var = "echo Data interval start:"
+
+ t2 = BashOperator(
+ task_id="fstring_templating_simple",
+ bash_command=f"{python_var} {{{{ ds }}}}",
+ dag=dag,
+ )
+
+This ensures the f-string processing results in a string containing the
literal double braces required by Jinja, which Airflow can then template
correctly before execution. Failure to do this is a common issue for beginners
and can lead to errors during DAG parsing or unexpected behavior at runtime
when the templating does not occur as expected.
