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The ord() function in Python takes a single character and returns its Unicode code point, an integer. chr() does the reverse, so the two always round-trip: I ran each example on Python 3.12.5 in a Windows Command Prompt, including the accented characters and symbols, so the numbers you see are exactly what Python returned. You’ll … Read more >>
The if else statement in Python runs one block of code when a condition is true and another block when it’s false. You write the condition after if, end the line with a colon, and indent what should run: Online-store rules like shipping tiers and sales tax make good examples, so that’s what I used. … Read more >>
Constants in Python are a convention, not a language feature: you name a variable in UPPER_CASE at module level, and everyone agrees not to change it. Python won’t stop a reassignment, but typing.Final lets a type checker catch one: One screenshot below shows mypy catching a Final violation that Python itself lets through; I used … Read more >>
reduce() in Python combines the items of an iterable into a single value by applying a two-argument function over and over: first to items one and two, then to that result and item three, and so on. It lives in functools: I printed the intermediate steps so you can watch reduce() work; the screenshots come … Read more >>
The sum() function in Python adds up the numbers in any iterable, such as a list, tuple, range or generator, and returns the total. An optional second argument sets the starting value: I ran every example on Python 3.12.5, and one of them on Python 3.11 too, because sum() changed how it adds floats in … Read more >>
A tuple of tuples in Python is a tuple whose items are themselves tuples, so you get rows of fixed values you can’t change. You build one with nested parentheses and read it with two indexes: These examples use a small table of US cities, and the screenshots come from Python 3.12.5 running in a … Read more >>
The len() function in Python returns how many items an object holds: characters in a string, elements in a list or tuple, keys in a dictionary. It works on any sequence or collection, and it’s instant, because Python stores the size rather than counting: Every output here comes from Python 3.12.5 in the Windows Command … Read more >>
You can install multiple Python versions side by side, each in its own folder. On Windows, the Python install manager (py install 3.11) adds versions and py -3.11 picks one. On any system, uv or pyenv install and switch them for you. For the screenshots, this machine has Python 3.12 from python.org plus 3.11 and … Read more >>
Environment variables in Python live in os.environ, a dictionary-like object. Read a required one with os.environ[“NAME”], an optional one with os.getenv(“NAME”, default), and check for one with “NAME” in os.environ: Every screenshot here is from the Windows Command Prompt running Python 3.12.5 with python-dotenv 1.2.4, and every variable is one I created for the demo. … Read more >>
Checking a variable’s type in Python takes one of two built-ins. type(x) tells you exactly what x is, and isinstance(x, SomeType) tells you whether it’s that type or a subclass of it: I tested everything below on Python 3.12.5 with NumPy 2.5.3; the screenshots are the real Command Prompt output. Use isinstance() for checks in … Read more >>