Python

To call an AI API from Python you install the provider’s SDK, read your API key from an environment variable, and send a prompt to a model such as OpenAI’s GPT-5 or Anthropic’s Claude Sonnet 5. The reply comes back as a Python object you can print, parse as JSON or write into a report. […]

The Python math module gives you the functions a calculator has and a spreadsheet takes for granted: square roots, logarithms, ceiling and floor, factorials, constants such as pi and e, and precise summation. Combined with the built-in round() and the decimal module for money, it covers almost every number you will meet in business scripts. […]

Python variables are named containers that hold a value, such as a price, a customer name or a list of invoices. You create a variable simply by assigning to it with =; there is no declaration step and no type keyword. This chapter covers how to name variables, how to assign them, how Python decides […]

Python booleans are the two values True and False. They are the answer to every yes-or-no question your program asks: is the invoice paid, is stock below the reorder level, does this list contain anything? Comparisons and conditions produce booleans, and Python also treats every other value as truthy or falsy, which this chapter explains. […]

Python with AI means writing, fixing and understanding Python code together with an AI assistant such as ChatGPT, Claude or GitHub Copilot. You describe the task in plain language, the assistant drafts the code, and you run, test and refine it. Used well, it removes the blank-page problem and teaches you idioms faster than searching […]

Python dates live in the built-in datetime module. It gives you date for a calendar day, datetime for a day plus time, timedelta for a duration, and strftime / strptime to convert between dates and text. Master those four and every due date, ageing report and month-end calculation becomes a few lines. Dates look simple […]

Python comments are notes inside your code that Python ignores when it runs the program. A single-line comment starts with #, a multi-line comment is several # lines or a triple-quoted string, and a docstring is a special string that documents a function or module. Good comments explain why, not what. Single-line comments with # […]

Python in Excel lets you run Python code directly inside a Microsoft 365 worksheet cell with the =PY() function. The code executes in the Microsoft Cloud, reads your ranges and tables through xl(), and returns a value, a pandas DataFrame or a chart to the grid, so you can combine Excel formulas with pandas and […]

A Python for loop walks through the items of a sequence one at a time and runs a block of code for each one. It works on lists, tuples, strings, dictionaries and anything else that is iterable. Combined with range(), enumerate() and zip(), the for loop is the workhorse of everyday data processing in Python. […]

Python string formatting is how you insert values into text and control how they look: two decimal places, thousands separators, percentages, padding and alignment. Modern code uses f-strings, written with an f before the opening quote, while the older format() method is still common in templates and existing projects. This chapter covers both with business-style […]