File Handling

Lesson

Part 1 — files, paths, modes and text files.

In this lesson you will

Part 1 at a glance

Concept

Why do we need files?

Data in variables live in memory and disappear when the program ends. A file keeps them on disk.

Comparison table: variables in memory are lost when a program ends and belong to one run, while data in a file persist, can be shared and can be large
Variables in memory (RAM)	Data in a file
Lost when the program ends	Kept after the program ends (persistent)
Belong to one run of one program	Can be read later or by other programs
Fast but limited in size	Stored on disk; can be very large

Concept

Table of the three kinds of file: text files store characters in lines, binary files store raw bytes such as pickled objects, and CSV files store comma-separated values; each with a typical use and how it is read
Kind	What it stores	Typical use	Read with
Text	Characters in lines ending with `\n`	Notices, logs, stories	`read()`, `readline()`, `readlines()`
Binary	Raw bytes, e.g. pickled Python objects	Records kept as lists or dictionaries	`pickle.load()`
CSV	Text lines of comma-separated values	Tables shared with spreadsheets	`csv.reader()`