How to Use Variable.get in Airflow: Simple Guide

Use Variable.get in Airflow to retrieve stored variables by their key name. It allows you to provide a default value if the variable is missing and can return the value as a string or parsed JSON.

Syntax

The Variable.get method has this syntax:

• key: The name of the variable to fetch.
• default_var: Optional value returned if the variable does not exist.
• deserialize_json: Optional boolean to parse the value as JSON if set to True.

python

Variable.get(key, default_var=None, deserialize_json=False)

Example

This example shows how to get a variable named my_var with a default fallback and JSON parsing:

python

from airflow.models import Variable

# Get a simple string variable
my_var = Variable.get('my_var', default_var='default_value')
print(f"Value of my_var: {my_var}")

# Get a JSON variable and parse it
my_json_var = Variable.get('my_json_var', default_var='{}', deserialize_json=True)
print(f"Parsed JSON variable: {my_json_var}")

Output

Value of my_var: default_value
Parsed JSON variable: {}

Common Pitfalls

Common mistakes include:

• Not providing default_var which causes an error if the variable is missing.
• Forgetting to set deserialize_json=True when expecting a JSON object, resulting in a string instead of a dictionary.
• Using incorrect variable keys that do not exist in Airflow's Variable store.

python

from airflow.models import Variable

# Wrong: No default_var, will raise KeyError if 'missing_var' does not exist
# missing_var = Variable.get('missing_var')

# Right: Provide default_var to avoid errors
missing_var = Variable.get('missing_var', default_var='fallback')

# Wrong: Forgetting to deserialize JSON
json_var = Variable.get('json_var')  # returns string

# Right: Deserialize JSON to get dict
json_var = Variable.get('json_var', deserialize_json=True)

Quick Reference

Remember these tips when using Variable.get:

• Always use default_var to avoid errors if the variable is missing.
• Use deserialize_json=True to get Python objects from JSON strings.
• Variable values are stored as strings in Airflow's backend.

Key Takeaways

Use Variable.get with the variable key to retrieve stored values in Airflow.

Always provide default_var to prevent errors if the variable is missing.

Set deserialize_json=True to automatically parse JSON strings into Python objects.

Variable values are stored as strings, so parsing is needed for complex data types.

Incorrect keys or missing defaults cause runtime errors.