__name__ and __main__ behavior in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code when run as a script?

Consider this Python script saved as script.py. What will it print when executed directly with python script.py?

Python

print(f"Top-level __name__ is: {__name__}")

if __name__ == "__main__":
    print("Running as main script")
else:
    print("Imported as a module")

A

Top-level __name__ is: __main__
Running as main script

B

Top-level __name__ is: script
Running as main script

C

Top-level __name__ is: __main__
Imported as a module

D

Top-level __name__ is: script
Imported as a module

💡 Hint

When a Python file is run directly, __name__ is set to "__main__".

When you run a Python file directly, its __name__ variable is set to "__main__". So the first print shows __main__, and the if condition is true, printing "Running as main script".

❓ Predict Output

intermediate

What is the output when this module is imported?

Given the same code below saved as module.py, what will be printed when another script imports it using import module?

Python

print(f"Top-level __name__ is: {__name__}")

if __name__ == "__main__":
    print("Running as main script")
else:
    print("Imported as a module")

A

Top-level __name__ is: __main__
Running as main script

B

Top-level __name__ is: module
Running as main script

C

Top-level __name__ is: module
Imported as a module

D

Top-level __name__ is: __main__
Imported as a module

💡 Hint

When a file is imported, __name__ is the module's name, not "__main__".

When imported, __name__ is the module's filename without .py, here "module". So the first print shows "module" and the else branch runs, printing "Imported as a module".

🔧 Debug

advanced

Why does this code print nothing when run directly?

This code is saved as test.py. When run with python test.py, it prints nothing. Why?

Python

def main():
    print("Hello from main")

if __name__ == "__main__":
    main

A Because __name__ is not "__main__" when run directly.

B Because main is referenced but not called (missing parentheses).

C Because print statement is inside a function that is never defined.

D Because the code has a syntax error and does not run.

💡 Hint

Check if the function main is actually executed.

The code references the function main but does not call it. It should be main() with parentheses to run the function and print the message.

📝 Syntax

advanced

Which option causes a SyntaxError?

Which of these code snippets will cause a SyntaxError when run?

A

if __name__ = "__main__":
    print("Running")

B

if __name__ == "__main__":
    print("Running")

C

)"gninnuR"(tnirp    
:"__niam__" == __eman__ fi

D

if __name__ == "__main__":
    print("Running")
else:
    print("Not main")

💡 Hint

Check the operator used in the if condition.

Option A uses a single equals sign (=) instead of double equals (==) in the if condition, which is invalid syntax in Python.

🚀 Application

expert

What is the output of this code when run directly?

Analyze this code saved as app.py. What will it print when executed with python app.py?

Python

def greet():
    print(f"Hello from {__name__}!")

if __name__ == "__main__":
    greet()
else:
    print(f"Imported module: {__name__}")

A No output

B Imported module: app

C Hello from app!

D Hello from __main__!

💡 Hint

Remember what __name__ is when running a script directly.

When run directly, __name__ is "__main__", so greet() prints "Hello from __main__!".