Stdlib Essentials

import json
payload = json.dumps({"ok": True})   # '{"ok": true}'
json.loads(payload)                  # {'ok': True}

from datetime import datetime, timezone
now = datetime.now(timezone.utc)
now.tzinfo is not None   # True
datetime(2020, 1, 1, tzinfo=timezone.utc).isoformat()
# '2020-01-01T00:00:00+00:00'

import logging, io
buf = io.StringIO()
logging.basicConfig(level=logging.INFO, stream=buf, force=True,
                    format="%(levelname)s %(message)s")
logging.getLogger("app").info("started")
"INFO started" in buf.getvalue()   # True

import argparse
p = argparse.ArgumentParser()
p.add_argument("--port", type=int, default=8000)
p.parse_args(["--port", "9000"]).port   # 9000
p.parse_args([]).port                   # 8000

import subprocess, sys
proc = subprocess.run([sys.executable, "-c", "print(1)"],
                      check=True, capture_output=True, text=True)
proc.stdout.strip()   # '1'

import re
EMAIL = re.compile(r"^[\w.+-]+@[\w-]+\.[\w.-]+$")
bool(EMAIL.match("a@b.co"))   # True
bool(EMAIL.match("nope"))     # False

from dataclasses import dataclass, asdict
@dataclass
class User:
    id: str
    name: str
asdict(User("1", "Ada"))   # {'id': '1', 'name': 'Ada'}

import hashlib
hashlib.sha256(b"hi").hexdigest()[:8]   # '8f434346'
len(hashlib.sha256(b"hi").hexdigest())  # 64

import secrets
tok = secrets.token_urlsafe(16)
len(tok) >= 16   # True

from urllib.parse import urlencode, urlparse
urlencode({"q": "python"})              # 'q=python'
urlparse("https://x.test/a?b=1").path   # '/a'

import csv, io
f = io.StringIO("id,name\n1,Ada\n")
rows = list(csv.DictReader(f))
rows[0]["name"]   # 'Ada'

from statistics import mean, median
mean([1, 2, 3])     # 2
median([1, 2, 3])   # 2

from functools import cache
@cache
def fib(n: int) -> int:
    return n if n < 2 else fib(n - 1) + fib(n - 2)
fib(10)   # 55

from enum import Flag, auto
class Perm(Flag):
    R = auto()
    W = auto()
bool(Perm.R | Perm.W)          # True
Perm.R in (Perm.R | Perm.W)    # True

import tomllib
tomllib.loads('x = 1\n')   # {'x': 1}