Category Built-in Methods

Python’s range() hands back a range object instead of a list of numbers, and that single choice explains the stop value that causes off-by-one loops. The object stores three integers and works out each element when something asks for it,…

I kept typing 7 // 3 and expecting 3. I had just switched from a language where integer division truncates toward zero, so floor division felt like a bug until I ran the numbers. Once I traced the three ceiling…

Python stops on the line the moment it meets && inside an if statement, and the caret lands under the second ampersand. Every C-family language accepts those two characters for logical conjunction, so a parser error reads like a bug…

Print the result of the Python map function and you get an address instead of a list, because nothing has run yet. The four numbers you passed in are still waiting inside an iterator, and the values only appear when…

The first time I wrote an event handler in Python, I passed a function to another function and could not figure out why it worked. The function I passed was not executed immediately – it was stored and called later…

I keep coming back to the Python sum() function whenever I need a quick way to add up numbers. It is one of those built-in tools that seems simple on the surface but has enough quirks to trip you up…

I ran into a situation last year where I had a pandas DataFrame with 50 columns and needed to pull out specific columns by their numerical position. The column names were generated programmatically and I had no way to know…

I’ve parsed more text files than I can count over the years – logs, configs, CSV exports, API responses saved to disk. The job is always the same: open the file, read the content, turn raw text into something my…

I have been working with text data for years, and I keep coming back to the same tool whenever I need to find or transform strings in Python. That tool is the re module. It is one of those things…