File modes in Python

Read, write, append, exclusive and binary — and what each one destroys.

from pathlib import Path

path = Path("modes.txt")
path.write_text("first\n", encoding="utf-8")

with open(path, "a", encoding="utf-8") as f:
    f.write("second\n")

with open(path, encoding="utf-8") as f:
    print(f.read().splitlines())

with open(path, "rb") as f:
    print(f.read()[:6])

try:
    open(path, "x")
except FileExistsError:
    print("x refuses to clobber")

How it works

1. w truncates; a appends; x refuses if the file exists.
2. b gives bytes instead of text, with no newline translation.
3. encoding should be explicit whenever text crosses machines.

Keywords and builtins used here

• as
• except
• open
• print
• try
• with

The run, in numbers

Lines

18

Characters to type

356

Tokens

123

Three-star pace

100 tpm

At the three-star pace of 100 tokens a minute, this run takes about 74 seconds.

Type this snippet

Step 3 of 3 in Errors in depth, step 64 of 72 in Language basics.

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