Virtual Environment For My First Python Program

Here We will create a virtual environment and code inside the environment.
So why virtual Environment?

to separate and isolate the packages we are using for different programs and projects.
working with code that depends on different versions of some library.
This issue happens a lot when dealing with Python 2 and Python 3.
Having different versions of packages installed can lead to a lot of confusion and bugs.

It’s much better to have separate environments for separate programs.

The module we use to create virtual environment here is called venv.

To create a virtual environment, We have to decide upon a directory where we want to place it. And run venv module as script with directory path.

Suppose we want to create a virtual environment at home/dev:
then change directory to the path as follows
```
 $cd home/dev
```

Now inside the directory we will run venv script:

     ~/dev$ python -m venv python-dev

What this does is:

creates python-dev directory if it doesn't exist
also creates directories inside it containing a copy of the python interpreter, the standard library and various supporting files.

Once we have created Virtual Environment, We have to activate it.

and in PowerShell,

     Scripts\Activate.ps1

     source python-dev/bin/activate

After activating, we can start programming.
now create main.py file.

if you have vs code installed then you can simply type code main.py in your terminal.
```
 ~/dev/python-dev $ code main.py
```

This opens a main.py file in vscode editor.
Now we can code our first Python Program Here.

     def main():
         print("hello world!")
     if __name__=="__main__":
         main() 
     else:
         print("file invoked")

Recursion Factorial