Glossary

Words from Maestro's courses on data and AI, each explained in a sentence or two.

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Altair: Altair (Vega-Altair) is a Python package for making charts by describing them: you say which column goes on each axis, color or size, and it writes the Vega-Lite that draws the chart.

Command Palette: The Command Palette is VS Code's search box for every command it has. Open it with Ctrl+Shift+P (Cmd+Shift+P on a Mac), type a few words and press Enter.
CSV: A CSV (comma-separated values) is a plain-text file that holds a table: one row per line, with commas between the columns.

Extension: An extension is an add-on you install in an app like VS Code to give it new abilities, such as running Python or opening notebooks.

Google Colab: Google Colab is a free Google service that runs Jupyter notebooks in your browser, with nothing to install. pandas and Altair come already installed.

JSON: JSON is a text format for structured data: labels and values inside curly braces, lists inside square brackets. Programs use it to pass data to each other.
Jupyter notebook: A Jupyter notebook is a file (ending in .ipynb) that mixes code, its results and notes in cells. You run one cell at a time and see its output right below it.

Log scale: A log scale is an axis where each equal step multiplies the value instead of adding to it, so 1,000, 10,000 and 100,000 sit evenly spaced.

Package: A package is a bundle of code someone else wrote that you install to give Python new tools. pandas and Altair are packages.
pandas: pandas is a Python package for working with tables of data, called DataFrames: loading them, filtering rows, picking columns and summarizing them.
Path: A path is a file's address on your computer: the folders you go through to reach it, ending in the file's name, like projects/python-for-altair/life_expectancy.csv.

Terminal: A terminal is a window where you type commands for your computer instead of clicking. You type a line, press Enter, and the computer answers in text.
Tuple: A tuple is a sequence of values in parentheses, like (16, 5). It works like a Python list that stays the same after it's made.

Vega-Lite: Vega-Lite is a language for describing charts in JSON: you name the data, the mark and which column goes on each axis, and a renderer draws it. Altair writes Vega-Lite for you.
Virtual environment: A virtual environment is a private set of Python packages for one project. What you install there stays there, so each project keeps the versions it needs.
VS Code: VS Code (Visual Studio Code) is a free code editor from Microsoft. With its Python and Jupyter extensions, it runs notebooks right inside the editor.

Working directory: The working directory is the folder a program treats as "here". A file name with no folders in front of it, like life_expectancy.csv, is looked for in that folder.