Reading and writing files in Python

File IO with with: open, use, and auto-close.

with open("notes.txt", "w") as f:
    f.write("first line\n")
    f.write("second line\n")

with open("notes.txt") as f:
    contents = f.read()

with open("notes.txt") as f:
    lines = [line.rstrip() for line in f]

with open("notes.txt", "a") as f:
    f.write("appended\n")

How it works

1. Mode "w" writes fresh; "a" appends.
2. read slurps everything; iterating yields lines.
3. The with block closes the file even on errors.

Keywords and builtins used here

• as
• for
• open
• with

The run, in numbers

Lines

12

Characters to type

257

Tokens

95

Three-star pace

100 tpm

At the three-star pace of 100 tokens a minute, this run takes about 57 seconds.

Type this snippet

Step 6 of 7 in Iterators, errors & files, step 49 of 72 in Language basics.

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Reading and writing files in other languages

• JavaScript