CPython Jython IronPython PyPy

• computers come with multiple versions of standard CPython pre-installed.

$python --version

python3 --version

python3 -m venv myenv

• here myenv is the name of virtual environment, we can give any name.

• Then activate the virtual environment

source myenv/bin/activate

#After this command, virtual env should start reflecting in 
#terminal like this

# (myenv) at the leftmost corner

• Deactivating a virtual environment:

deactivate

• before this upgrade pip using following command:

pip install --upgrade pip

• After this install requirements from requirements.txt file:
• make sure your virtual env is activated.

pip install -r requirements.txt

• here -r is for recursive.

Once requirements are installed, we are good to go.

• on the go if we change requirements or add new dependencies we need to keep modifying this file.

• we can generate this file from venv directly using following command:

pip freeze > requirements.txt

• make sure venv is active so that dependencies are being picked from there only rather than global python packages.