Numbers, Strings & Operators

With variables and types covered, it's time to actually do something with them. Numbers and strings are the two types you'll manipulate the most, and Python gives each a set of operators worth knowing cold.

The two operators new programmers usually haven't seen before are // and %. Floor division (//) divides and rounds down to the nearest whole number - useful whenever you need a count of "how many whole groups fit," like splitting items evenly across pages. Modulo (%) gives you what's left over after that division - useful for anything cyclical, like checking if a number is even (n % 2 == 0) or wrapping an index around the length of a list.

Strings can be written with either single or double quotes - Python treats them identically, so pick whichever avoids escaping (a string containing an apostrophe is easier to write with double quotes, and vice versa). The + operator between two strings concatenates them rather than adding numbers. len() works on strings too - it returns the character count, including spaces.

Indexing starts at 0, not 1 - word[0] is the first character. Negative indices count backward from the end, so word[-1] is always the last character no matter how long the string is, which is far more common in real Python code than computing len(word) - 1 yourself. Indexing past either end (word[100] on a 6-character string) raises an IndexError - Python won't silently return something wrong.

An f-string is a string literal prefixed with f, where anything inside curly braces gets evaluated and dropped into the text. It's the cleanest way to build a string out of variables - no manual + concatenation needed. This is just a preview; the next chapter covers f-string formatting in real depth.