Input, Output & String Formatting

print() and input() are how a program talks to whoever is running it. You won't use input() much inside Forge Algorithm Lab levels, since the grader calls your functions directly rather than typing at a prompt - but understanding it is fundamental to Python, and print() remains the tool you'll reach for constantly while debugging.

print() accepts any number of arguments, joins them with a space by default (controllable via sep), and adds a newline at the end by default (controllable via end). Overriding end is a common trick for building up output across multiple print() calls without new lines splitting them apart.

input() prints its argument as a prompt, waits for the user to type something and press Enter, and returns whatever they typed - always as a str, even if they typed digits. That's a common early bug: age = input("...") gives you the string "36", and "36" + 1 raises a TypeError because you can't add a string and an int. You have to explicitly convert it first, with int() or float().

The part after the colon inside {} is a format spec. .2f means "as a fixed-point float, 2 digits after the decimal" - essential for anything involving money or percentages, where "19.9" reading as "$19.90" matters. The comma adds thousands separators, > and < control alignment, and a leading zero with a width (like 04d) zero-pads integers - handy for things like formatted IDs or times.

f-strings are the modern, recommended way to format strings, but you'll run into two older styles when reading existing code - worth recognizing even if you rarely write them yourself: