File Handling

Python reads and writes files with built-in functions. The key function is open().

Open a file

python
f = open("demofile.txt")

Modes for open()

The second argument selects a mode:

Combine them, like "rb" for read binary.

The "x" create mode

python
f = open("newfile.txt", "x")

### errors if the file exists

The "a" append mode

python
f = open("demofile.txt", "a")
f.write("Now the file has more content!")

Adds to the end without deleting what's there.

The "w" write mode

python
f = open("demofile.txt", "w")
f.write("Whoops! I deleted the content!")

Overwrites everything, or creates the file if it's missing.

Always close files

python
f.close()

The with statement (recommended)

with closes the file for you automatically:

python
with open("demofile.txt") as f:
    content = f.read()

TL;DR

• open(filename, mode) opens a file.
• Modes: r read, a append, w write, x create.
• Add t for text (default) or b for binary.
• Always close files; with does it automatically.