Related values often arrive in separate lists, such as names in one list and scores in another. Python’s zip() function pairs items at matching positions and returns an iterator that yields tuples. I’ll explain what zip() returns and show how…
A file that already contains notes can be a place to add another line without losing what’s there. Python’s append mode writes new text at the end, while other modes can create or replace a file. I’ll explain how the…
A class may need to show a value that changes with its other data, and callers may still read it with dot notation. Python’s property decorator lets a class expose a method as an attribute that can compute a value…
When a list of records includes entries that pass a condition and entries that do not, selecting the matches calls for a test. Python’s filter() applies a test, called a predicate, to each item and returns an iterator containing the…
An unfamiliar Python value can leave you unsure what operations it supports. type() reports the value’s class, which defines what its instances can do, or creates a class when called with three arguments. I’ll walk through both forms of type()…
A function like sorted() can take code you supply, such as a rule for how to compare items. A callback is a function you pass to another function, which then calls it while doing its work. In this piece, I’ll…
Ordering a list of scores or names in Python doesn’t require writing your own sorting routine. The built-in sorted() returns a new list of the items in order and leaves the original unchanged. I’ll walk you through sorting in either…
Importing a module makes Python look through a list of folders to find it. PYTHONPATH is an environment variable, a setting your shell passes to programs, that adds extra folders to that list when Python starts. This guide shows you…
Python picks (5, 8) over (5, 2). I value getting one winner without asking Python to order every candidate. When the candidates are records, you may need the winning object for its other fields. Follow max()’s result for a record…
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,…
