Task dependencies (>> and << operators) in Apache Airflow - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set task1 to run before task2 using the >> operator.

Apache Airflow

task1 [1] task2

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

A>>

B-

C+

D<<

Attempts:

3 left

💡 Hint

Common Mistakes

Using << instead of >> reverses the order.

The >> operator sets the left task to run before the right task.

2fill in blank

medium

Complete the code to set task3 to run after task4 using the << operator.

Apache Airflow

task3 [1] task4

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

A-

B>>

C<<

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using >> instead of << reverses the dependency.

The << operator sets the left task to run after the right task.

3fill in blank

hard

Fix the error in the code to correctly set taskA to run before taskB.

Apache Airflow

taskA [1] taskB

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

A>>

B+

C<<

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing << and >> operators.

To set taskA before taskB, use >>. Using << reverses the order.

4fill in blank

hard

Fill both blanks to set taskX to run before taskY and taskY to run before taskZ.

Apache Airflow

taskX [1] taskY [2] taskZ

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

A>>

B<<

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing << and >> operators incorrectly.

Using >> sets the order: taskX before taskY, and taskY before taskZ.

5fill in blank

hard

Fill all three blanks to set task1 before task2, task3 after task2, and task4 before task3.

Apache Airflow

task1 [1] task2
 task3 [2] task2
 task4 [3] task3

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

A>>

B<<

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing the direction of << and >> operators.

Use >> for 'before' and << for 'after' to set correct dependencies.

Practice

1. In Airflow, what does the operator task1 >> task2 mean?

easy

A. task1 runs before task2

B. task1 runs after task2

C. task1 and task2 run at the same time

D. task1 is unrelated to task2

Solution

1. Step 1: Understand the meaning of >> operator

   The >> operator in Airflow means "runs before" or "upstream to downstream" dependency.

2. Step 2: Apply to given tasks

   Given task1 >> task2, task1 must finish before task2 starts.

3. Final Answer:

   task1 runs before task2 -> Option A

4. Quick Check:

   >> means runs before [OK]

Hint: Remember: >> means runs before, << means runs after [OK]

Common Mistakes:

• Confusing >> with <<
• Thinking >> means runs after
• Assuming tasks run in parallel

2. Which of the following is the correct syntax to set task2 to run after task1 using Airflow operators?

easy

A. task1 >> task2

B. task2 << task1

C. task2 >> task1

D. task1 << task2

Solution

1. Step 1: Identify the operator meaning

   >> means "runs before"; so task1 >> task2 means task1 runs before task2.

2. Step 2: Match the requirement

   To make task2 run after task1, task1 must run before task2, so task1 >> task2 is correct.

3. Final Answer:

   task1 >> task2 -> Option A

4. Quick Check:

   task2 after task1 = task1 >> task2 [OK]

Hint: Use >> to say runs before, so task1 >> task2 means task2 after task1 [OK]

Common Mistakes:

• Using << backwards
• Swapping task order
• Confusing which task is upstream

3. Given the code snippet:

task1 >> task2 << task3

Which statement is true about the task execution order?

medium

A. task2 runs before task1 and task3

B. task1 runs after task2, and task3 runs after task2

C. task1 runs before task2, and task3 runs before task2

D. task1, task2, and task3 run in parallel

Solution

1. Step 1: Break down the dependencies

   task1 >> task2 means task1 runs before task2; task3 << task2 means task3 runs before task2 (because << means runs after, so task2 runs after task3).

2. Step 2: Combine the relations

   Both task1 and task3 must finish before task2 starts.

3. Final Answer:

   task1 runs before task2, and task3 runs before task2 -> Option C

4. Quick Check:

   task1 and task3 before task2 = task1 runs before task2, and task3 runs before task2 [OK]

Hint: >> means runs before; << means runs after (reverse order) [OK]

Common Mistakes:

• Misreading << as runs before
• Assuming task2 runs first
• Thinking tasks run in parallel

4. Identify the error in this Airflow task dependency code:

task1 >> >> task2

medium

A. task2 runs before task1

B. Syntax error due to double >> operators

C. No error, tasks run sequentially

D. task1 and task2 run in parallel

Solution

1. Step 1: Analyze the operator usage

   The code has two consecutive >> operators without a task in between, which is invalid syntax in Python and Airflow.

2. Step 2: Understand Airflow dependency syntax

   Only one >> operator is allowed between two tasks to set dependency; double >> causes syntax error.

3. Final Answer:

   Syntax error due to double >> operators -> Option B

4. Quick Check:

   Double >> is invalid syntax [OK]

Hint: Only one >> or << between tasks, no doubles [OK]

Common Mistakes:

• Writing multiple >> operators in a row
• Ignoring syntax errors
• Assuming double >> means stronger dependency

5. You want to create a DAG where task1 and task3 run first in parallel, then task2 runs after both finish. Which code correctly sets this dependency?

hard

A. task2 >> [task1, task3]

B. task1 << task2 >> task3

C. task1 >> task2 >> task3

D. [task1, task3] >> task2

Solution

1. Step 1: Understand the requirement

   task1 and task3 run in parallel first, then task2 runs after both finish.

2. Step 2: Translate to Airflow syntax

   Using list syntax [task1, task3] >> task2 means both task1 and task3 run before task2.

3. Step 3: Check other options

   task1 >> task2 >> task3 runs tasks sequentially; B and D have wrong directions.

4. Final Answer:

   [task1, task3] >> task2 -> Option D

5. Quick Check:

   List >> task means all list tasks before next [OK]

Hint: Use list syntax [task1, task3] >> task2 for parallel upstream tasks [OK]

Common Mistakes:

• Using >> in wrong order
• Not using list for parallel tasks
• Confusing << with >>