Setting up virtual environments in Python

Virtual Environment in Python

When building applications using any programming language, we sometimes use codes provided by the programming community.

In Python, without an isolated environment newer version of a particular package will replace older ones and this will in turn 
lead to breaking changes for the project that depends on the older package.

To handle this problem, Python provides us a tool(venv) to create an isolated environment for our project dependencies.

When we install a package, we do not want it to be installed on the global path for site packages; we want that package to be 
isolated and constrained to the application that needs it.

We can see where system libraries (libraries that are bundled into the python language such as math, string, etc) are installed
on your system using:
```
import sys

print(sys.prefix)

```

To see where third party packages are installed, use:
```
import sitepackages 

print(site.getsitepackages())
```

## How to create a virtual environment 

Assuming you have a project named hello, this is how you will create and activate a virtual environment before installing any
package:
If you do not have the package for creating a virtual environment on your system, then install it using : 
python3 -m pip install virtualenv 

1. Create a directory for your project and change into that directory

```
mkdir hello
cd hello

```

2. Create the virtual environment.

Assuming you want to name your virtual environment "env", you will use any of the commands below to create an environment.

If your command was successful, a directory will be created within hello for you.

```
python3 -m venv env 

or

python -m venv env 

or 

py -m venv env

```

3. Now to activate the environment, it depends on which OS you are using.

For Mac or Linux , do :
```
source env/bin/activate 
```

For windows , do:

```
.\Scrips\activate

```

Now,once the environment has been activated, you will see the environment name enclosed within parentheses on the terminal.

You can now go ahead to install packages.

Let us install flask.

``` python -m pip install flask```

You can create a requirements.txt file to hold information about your packages using : 

python3 -m pip freeze > requirements.txt 

Then to install the dependencies, use : 

python3 -m pip install -r requirements.txt 

If you encounter any problem, drop a comment below .

Thank you