Jinja-based templating generates dynamic text by evaluating expressions embedded in a template. In Airflow, it fills task arguments at run time with values from the task context, such as logical_date, instead of hardcoding dates or paths. section 5.2.1 section 5.5
Date-partitioned event files
A BashOperator can write each execution’s API response to a date-specific file: `curl -o /data/events/{{ logical_date | ds }}.json ...`. A downstream PythonOperator can receive matching input and output paths through `op_kwargs`, such as `/data/events/{{logical_date | ds}}.json` and `/data/stats/{{logical_date | ds}}.csv`. section 3.3.1
Practical details shape how templates behave:
- Use double curly braces, such as `{{ name }}` or `{{ logical_date }}`, to insert runtime values. section 5.2.1
- Format datetime components inside templates when external names require padding, for example `{{ '{:02}'.format(data_interval_start.hour) }}`. section 5.2.1
- Check an operator’s templated-attribute allowlist; unsupported arguments preserve template text literally. section 5.2.1
- Treat PythonOperator differently: pass run-time values through `op_args` or `op_kwargs`, rather than expecting its callable variables to be Jinja-rendered. section 5.5
Listing 3.4 Using templating to specify dates
fetch_events = BashOperator(
task_id="fetch_events",
bash_command=(
"mkdir -p /data/events && "
"curl -o /data/events/{{ logical_date | ds }}.json" #1
"'http://events-api:8081/events/latest"
),
)
Shows a complete BashOperator command that renders logical_date into a daily output filename. section 3.3.1
