Pushing and pulling XCom values in Apache Airflow - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to push an XCom value in an Airflow task.

Apache Airflow

def push_function(ti):
    ti.[1](key='sample_key', value='sample_value')

Drag options to blanks, or click blank then click option'

Apull_xcom

Bpush_xcom

Cxcom_pull

Dxcom_push

Attempts:

3 left

💡 Hint

Common Mistakes

Using pull methods instead of push.

Incorrect method names like push_xcom.

The method xcom_push is used to push a value to XCom in Airflow.

2fill in blank

medium

Complete the code to pull an XCom value inside a task.

Apache Airflow

def pull_function(ti):
    value = ti.[1](key='sample_key', task_ids='push_task')

Drag options to blanks, or click blank then click option'

Axcom_push

Bxcom_pull

Cpull_xcom

Dpush_xcom

Attempts:

3 left

💡 Hint

Common Mistakes

Using push methods instead of pull.

Incorrect method names like pull_xcom.

The method xcom_pull is used to retrieve a value from XCom in Airflow.

3fill in blank

hard

Complete the code to push an XCom value in an Airflow task.

Apache Airflow

def push_function(ti):
    ti.[1]('sample_key', 'sample_value')

Drag options to blanks, or click blank then click option'

Axcom_push

Bpush_xcom

Cxcom_pull

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using pull methods instead of push.

Incorrect method names like push_xcom.

The method xcom_push is used to push a value to XCom in Airflow.

4fill in blank

hard

Fill both blanks to push and then pull an XCom value correctly.

Apache Airflow

def task_function(ti):
    ti.[1](key='key1', value='value1')
    pulled_value = ti.[2](key='key1', task_ids='task_function')

Drag options to blanks, or click blank then click option'

Axcom_push

Bxcom_pull

Cpush_xcom

Dpull_xcom

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up push and pull methods.

Using incorrect method names.

Use xcom_push to push and xcom_pull to pull XCom values.

5fill in blank

hard

Fill all three blanks to push a value, pull it, and print it inside an Airflow task.

Apache Airflow

def task_function(ti):
    ti.[1](key='my_key', value='my_value')
    value = ti.[2](key='my_key', task_ids='task_function')
    print([3])

Drag options to blanks, or click blank then click option'

Axcom_push

Bxcom_pull

Cvalue

Dmy_value

Attempts:

3 left

💡 Hint

Common Mistakes

Printing the string literal instead of the variable.

Using wrong method names.

Push with xcom_push, pull with xcom_pull, then print the pulled variable value.

Practice

1. What is the main purpose of using xcom_push and xcom_pull in Airflow?

easy

A. To share small pieces of data between tasks in a workflow

B. To schedule tasks to run at specific times

C. To create new DAGs dynamically

D. To monitor task execution logs

Solution

1. Step 1: Understand the role of XComs

   XComs are designed to let tasks exchange small data pieces during workflow execution.

2. Step 2: Identify the functions' purpose

   xcom_push sends data, and xcom_pull retrieves it between tasks.

3. Final Answer:

   To share small pieces of data between tasks in a workflow -> Option A

4. Quick Check:

   Data sharing = A [OK]

Hint: Remember: push sends data, pull gets data [OK]

Common Mistakes:

• Confusing XComs with scheduling tasks
• Thinking XComs create DAGs
• Assuming XComs handle logs

2. Which of the following is the correct syntax to push a value '42' with key 'result' inside a task instance ti?

easy

A. xcom_push(ti, 'result', 42)

B. ti.push_xcom('result', 42)

C. ti.xcom_pull(key='result', value=42)

D. ti.xcom_push(key='result', value=42)

Solution

1. Step 1: Recall the method signature

   The correct method to push data is ti.xcom_push(key=..., value=...).

2. Step 2: Check each option

   ti.xcom_push(key='result', value=42) matches the correct syntax. Options A and B use wrong method names or argument order. ti.xcom_pull(key='result', value=42) uses xcom_pull which is for pulling, not pushing.

3. Final Answer:

   ti.xcom_push(key='result', value=42) -> Option D

4. Quick Check:

   Push syntax = C [OK]

Hint: Push uses ti.xcom_push(key=..., value=...) [OK]

Common Mistakes:

• Using wrong method names like push_xcom
• Confusing push with pull
• Incorrect argument order

3. Given the following code snippet inside a task:

ti.xcom_push(key='data', value=100)
value = ti.xcom_pull(key='data')

What will be the value of the variable value after execution?

medium

A. None

B. KeyError

C. 100

D. 'data'

Solution

1. Step 1: Understand the push operation

   The code pushes the integer 100 with key 'data' into XCom storage.

2. Step 2: Understand the pull operation

   The code pulls the value stored with key 'data', which is 100.

3. Final Answer:

   100 -> Option C

4. Quick Check:

   Push 100, pull 100 = D [OK]

Hint: Pull returns the value pushed with the same key [OK]

Common Mistakes:

• Expecting pull to return None if key exists
• Confusing key with value
• Assuming pull raises error if key exists

4. You wrote this code inside a task:

ti.xcom_push('result', 10)
value = ti.xcom_pull(key='result')

But value is always None. What is the likely problem?

medium

A. The xcom_push call is missing keyword arguments

B. The key 'result' does not exist in XCom

C. You must call xcom_pull before xcom_push

D. XComs cannot store integers

Solution

1. Step 1: Check the xcom_push syntax

   The method requires keyword arguments: key= and value=. Passing positional arguments causes failure.

2. Step 2: Understand the effect of wrong syntax

   Because the push failed silently, the key 'result' was never stored, so pull returns None.

3. Final Answer:

   The xcom_push call is missing keyword arguments -> Option A

4. Quick Check:

   Push needs key= and value= [OK]

Hint: Always use key= and value= in xcom_push [OK]

Common Mistakes:

• Using positional arguments in xcom_push
• Assuming pull before push order matters
• Thinking XComs can't store integers

5. You want to pass a dictionary from one task to another using XCom. Which code snippet correctly pushes and pulls the dictionary {'a': 1, 'b': 2}?

hard

A. ti.xcom_push('my_dict', {'a': 1, 'b': 2})
data = ti.xcom_pull('my_dict')

B. ti.xcom_push(key='my_dict', value={'a': 1, 'b': 2})
data = ti.xcom_pull(key='my_dict')

C. ti.xcom_push(value={'a': 1, 'b': 2}, key='my_dict')
data = ti.xcom_pull(key='my_dict')

D. ti.xcom_push(key='my_dict', value='{'a': 1, 'b': 2}')
data = ti.xcom_pull(key='my_dict')

Solution

1. Step 1: Verify correct xcom_push syntax with dictionary

   ti.xcom_push(key='my_dict', value={'a': 1, 'b': 2}) data = ti.xcom_pull(key='my_dict') uses correct keyword arguments key= and value= with a dictionary value.

2. Step 2: Check other options for errors

   ti.xcom_push(value={'a': 1, 'b': 2}, key='my_dict') data = ti.xcom_pull(key='my_dict') uses non-standard keyword argument order; ti.xcom_push('my_dict', {'a': 1, 'b': 2}) data = ti.xcom_pull('my_dict') uses positional args which is incorrect; ti.xcom_push(key='my_dict', value='{'a': 1, 'b': 2}') data = ti.xcom_pull(key='my_dict') passes dictionary as a string with wrong quotes causing syntax error.

3. Final Answer:

   ti.xcom_push(key='my_dict', value={'a': 1, 'b': 2}) data = ti.xcom_pull(key='my_dict') -> Option B

4. Quick Check:

   Push dict with key= and value= [OK]

Hint: Use key= and value= with dict, avoid string quotes errors [OK]

Common Mistakes:

• Using positional arguments in xcom_push
• Passing dict as a string with wrong quotes
• Mixing argument order incorrectly