Read, write and organise files and folders — Python Chapter 3

$ run as a normal user# run as root (or with sudo)

Work with paths

Path objects join paths safely and have methods for everything.

paths.py

from pathlib import Path
 
home = Path.home()
logs = Path("/var/log")
conf = Path("/etc") / "ssh" / "sshd_config"
 
print(conf.name, conf.suffix, conf.parent, conf.exists(), conf.is_file())
for p in logs.glob("*.log"):
    print(p, p.stat().st_size)
for p in Path("/etc").rglob("*.repo"):
    print(p)

3.2

Read and write text files

with open(...) closes the file by itself, also after an error.

read_write.py

from pathlib import Path
 
with open("/etc/hosts", encoding="utf-8") as f:
    for line in f:
        if line.strip() and not line.startswith("#"):
            print(line.rstrip())
 
report = Path("/tmp/report.txt")
report.write_text("disk OK\n", encoding="utf-8")
with report.open("a", encoding="utf-8") as f:
    f.write("memory OK\n")
print(report.read_text(encoding="utf-8"))

Mode	Meaning
`"r"`	Read (default)
`"w"`	Write — empties the file first
`"a"`	Append to the end
`"x"`	Create; fail if it exists
`"rb"`, `"wb"`	Binary

3.3

Copy, move and delete

shutil does the file work of cp, mv and rm -r.

organise.py

import shutil
from pathlib import Path
 
src = Path("/srv/www")
backup = Path("/backup/www-copy")
shutil.copytree(src, backup, dirs_exist_ok=True)
shutil.copy2("/etc/hosts", "/backup/hosts")
shutil.move("/tmp/report.txt", "/backup/report.txt")
shutil.rmtree("/tmp/old-build", ignore_errors=True)
Path("/backup/logs").mkdir(parents=True, exist_ok=True)

Watch out

shutil.rmtree deletes without asking. Print the path first, and never build it from user input without checks.

3.4

Clean up old files

Find files older than N days and delete (or archive) them.

cleanup.py

import time
from pathlib import Path
 
days = 14
cutoff = time.time() - days * 86400
for p in Path("/var/tmp/app").rglob("*"):
    if p.is_file() and p.stat().st_mtime < cutoff:
        print("deleting", p)
        p.unlink()

3.5

Make archives

shutil.make_archive and tarfile pack folders like tar.

archive.py

import shutil
import tarfile
from datetime import date
 
name = shutil.make_archive(f"/backup/etc-{date.today()}", "gztar", root_dir="/etc")
print(name)
 
with tarfile.open(name) as t:
    print(len(t.getnames()), "files in the archive")