__name__ and __main__ behavior in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the value of __name__ when a Python script is run directly?

When a Python script is run directly, the value of __name__ is "__main__". This means the script is the main program being executed.

beginner

What does the condition if __name__ == "__main__": do in a Python script?

This condition checks if the script is being run directly (not imported). If true, the code inside the block runs. It helps separate code that should only run when the script is the main program.

beginner

What is the value of __name__ when a Python file is imported as a module?

When a Python file is imported as a module, __name__ is set to the module's name (usually the filename without .py). It is not "__main__".

intermediate

Why is using if __name__ == "__main__": useful in Python scripts?

It allows the script to be used both as a reusable module and as a standalone program. Code inside this block runs only when the script is executed directly, preventing it from running during import.

beginner

Example: What will this code print if saved as example.py and run directly?<br>

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

Output will be:<br>

__main__
Running directly

<br>Because the script runs directly, __name__ is "__main__" and the condition is true.

What does __name__ equal when a Python file is imported as a module?

A "__main__"

B None

C The module's filename without .py

D An empty string

When imported, __name__ is set to the module's name, usually the filename without the .py extension.

What happens to code inside if __name__ == "__main__": when the script is imported?

A It runs immediately

B It causes an error

C It runs only if called explicitly

D It does not run automatically

Code inside this block runs only when the script is executed directly, not when imported.

Why do Python programmers use if __name__ == "__main__":?

A To run code only when script runs directly

B To prevent syntax errors

C To run code only when imported

D To define global variables

This condition ensures code runs only when the script is the main program, not when imported.

If you run a Python script directly, what will print(__name__) output?

A The script's filename

B "__main__"

C An error

D Nothing

When run directly, __name__ is set to "__main__".

What is the main benefit of using if __name__ == "__main__": in a Python file?

A To allow the file to be both a module and a script

B To make the script run faster

C To avoid import errors

D To automatically run tests

It allows the file to be imported without running main code, and also run as a standalone script.

Explain what __name__ and __main__ mean in a Python script and why they are important.

Think about how Python knows if a file is run directly or imported.

Describe a real-life scenario where using if __name__ == '__main__': helps in organizing Python code.

Imagine you want to share functions but also test them in the same file.