General

Python is a scripting language.

Scripts are any *.py file executed by an interpreter (like Python’s IDLE). Package is a collection of modules/scripts installed by a package manager.

Python in Windows

PATH is an environment variable in Windows. It basically tells the commandline what folders to look in when attempting to find a file. If you didn’t add Python to PATH then you would call it from the commandline like this:

C:/Python27/Python some_python_script.py

Whereas if you add it to PATH, you can do this:

python some_python_script.py

• Open command prompt
• Enable Python environment (ensure Python installed beforehand): python
• This will show up: >>>

Sample code with Python in Command Prompt:

>>> print(‘Hello World!’) Hello World! >>> 2 + 57 59

To exit Python environment: quit() or exit() or ctrl+z (and enter)

To run *.py (e.g. abc.py),
In Command Prompt, :: Exit Python environment (if in it) :: Go to directory of abc.py :: Type and press enter: python abc.py	In IDLE, :: Open abc.py in IDLE :: Run (press F5)

To find where python is installed, execute in cmd: where python

# save as xz.py def add(x, z): result = x + z return result	# save as addxz.py import xz xz.add(3,4) # when run addxz.py , output will be 7

Check python version: python –version

If version still shows the previous, update to latest @ PATH by Moving Up.

Python’s Packages

PIP

PIP is Python’s package manager.

# Check PIP version
pip --version

# Download and install packages like TensorFlow and camelcase
pip install <packagename>

# Using package
import camelcase
c = camelcase.CamelCase()

Package

# Useful packages list
pip install jupyterlab # jupyterlab; launch with: jupyter-lab
pip install notebook # classic Jupyter notebook; launch with: jupyter notebook

Python Repository

Unknowns

venv / pyvenv	single Python version
pyenv	multiple Python version (deprecated @ Python 3.8+ and replaced with venv)
pyenv-virtualenv	Python 2 inclusive

venv

$ python3 -m venv directory-name-to-create
# e.g. python3.6 -m venv example-three-six

$ source name-given/bin/activate

$ deactivate

$ rm -r name-given

When the environment is active, any packages can be installed to it via pip as normal (by default, the newly created environment will not include any packages).