---
title: Python Main function - Python Cheatsheet
description: is the name of the scope in which top-level code executes. A module’s name is set equal to main when read from standard input, a script, or from an interactive prompt.
---

<base-title :title="frontmatter.title" :description="frontmatter.description">
Main top-level script environment
</base-title>

## What is it

`__main__` is the name of the scope in which top-level code executes.
A module’s **name** is set equal to `__main__` when read from standard input, a script, or from an interactive prompt.

A module can discover whether it is running in the main scope by checking its own `__name__`, which allows a common idiom for conditionally executing code in a module. When it is run as a script or with `python -m` but not when it is imported:

```python
>>> if __name__ == "__main__":
...     # execute only if run as a script
...     main()
```

For a package, the same effect can be achieved by including a **main**.py module, the contents of which will be executed when the module is run with -m.

For example, we are developing a script designed to be used as a module, we should do:

```python
>>> def add(a, b):
...     return a+b
...
>>> if __name__ == "__main__":
...     add(3, 5)
```

## Advantages

1. Every Python module has it’s `__name__` defined and if this is `__main__`, it implies that the module is run standalone by the user, and we can do corresponding appropriate actions.
2. If you import this script as a module in another script, the **name** is set to the name of the script/module.
3. Python files can act as either reusable modules, or as standalone programs.
4. `if __name__ == "__main__":` is used to execute some code only if the file is run directly, and is not being imported.