Python · Chapter 26 of 45

Python File Handling

Open a file with `open(path, mode)` and always close it — or use `with` which closes automatically.

Modes: `r` read, `w` write (overwrite), `a` append, `b` binary.

with open() as ...

The recommended pattern. Guarantees the file is closed even if an error occurs.

`read()` grabs everything; `readlines()` gets a list of lines; iterating a file yields one line at a time (memory-friendly).

Example 1 (python)

with open("hello.txt", "w") as f:
    f.write("Hello\nWorld")

with open("hello.txt") as f:
    print(f.read())

Output

Hello
World

Write then read the same file.

Example 2 (python)

with open("data.txt") as f:
    for line in f:
        print(line.strip())

Output

line 1
line 2

Iterate line-by-line — memory efficient for big files.

💡 Note: Use encoding="utf-8" explicitly when reading/writing text files — defaults differ across operating systems.