Belajar Python

python3 --version
Python 3.12.4

# Ini komentar — diabaikan oleh Python
print("Halo dari Python!")
print("umur:", 17, "tahun")

# String tiga kutip untuk multi-baris:
print("""
Baris pertama
Baris kedua
""")

# main.py
print("Mode skrip:", __name__)

if __name__ == "__main__":
    print("Ini hanya jalan saat dieksekusi langsung.")

nama = "Ari"
umur = 17
tinggi = 168.5
aktif = True

print(type(nama), type(umur), type(tinggi), type(aktif))

# konversi
teks = "42"
angka = int(teks)
print(teks + "5")    # string: "425"
print(angka + 5)     # int: 47

# input selalu string
masukan = input("Umur: ")
umur = int(masukan)
print(f"Tahun depan: {umur + 1}")

a, b = 7, 2
print(a / b)    # 3.5 — selalu float
print(a // b)   # 3 — dibulatkan ke bawah
print(a % b)    # 1 — sisa
print(a ** b)   # 49 — pangkat

print(a > b and b > 0)   # True
print(not a > b)          # False

counter = 10
counter += 5  # 15
counter **= 2 # 225

nilai = 82

if nilai >= 90:
    print("A")
elif nilai >= 80:
    print("B")
elif nilai >= 70:
    print("C")
else:
    print("D")

# ternary
status = "lulus" if nilai >= 70 else "remedial"
print(status)

# chaining
umur = 25
print(13 <= umur <= 19)  # False — bukan remaja

# range dasar
for i in range(5):
    print(i, end=" ")   # 0 1 2 3 4
print()

# range dengan awal, akhir, langkah
for n in range(10, 0, -2):
    print(n, end=" ")   # 10 8 6 4 2
print()

# enumerate: indeks + elemen
buah = ["apel", "mangga", "jeruk"]
for i, nama in enumerate(buah):
    print(f"{i}: {nama}")

# for-else
target = 7
for n in range(10):
    if n == target:
        print(f"ketemu: {n}")
        break
else:
    print("tidak ditemukan")

# baca angka sampai 0
total = 0
while True:
    teks = input("Angka (0=berhenti): ")
    n = int(teks)
    if n == 0:
        break
    total += n

print(f"Total: {total}")

# continue: lewati bilangan ganjil
for i in range(10):
    if i % 2 == 1:
        continue
    print(i, end=" ")  # 0 2 4 6 8

s = "  Belajar Python itu seru  "
bersih = s.strip()
print(len(bersih))
print(bersih.upper())
print(bersih.split(" "))
print(bersih.replace("seru", "mantap"))
print(bersih.startswith("Belajar"))

# iterasi karakter
for c in "halo":
    print(c, end="-")  # h-a-l-o-
print()

# string mentah
print(r"C:\folder\baru")  # backslash tetap utuh

nama, umur, tinggi = "Ari", 17, 168.5

# f-string dengan format
print(f"Nama: {nama}, umur: {umur}, tinggi: {tinggi:.1f} cm")

# align
print(f"{nama:>10} |")
print(f"{nama:<10} |")
print(f"{nama:^10} |")

# ribuan
harga = 1234567
print(f"Rp{harga:,}")

# join
buah = ["apel", "mangga", "jeruk"]
print(", ".join(buah))

# debug cepat
print(f"{harga=}")

buah = ["apel", "mangga", "jeruk"]
buah.append("pisang")
buah.insert(1, "anggur")
buah.remove("jeruk")
print(buah)
print(len(buah), "apel" in buah)

# reference vs copy
a = [1, 2, 3]
b = a          # reference — bukan salinan
b.append(4)
print(a)        # [1, 2, 3, 4] — a ikut berubah!

c = a.copy()   # salinan asli
c.append(5)
print(a)        # [1, 2, 3, 4] — a aman

# dasar
kuadrat = [x**2 for x in range(1, 6)]
print(kuadrat)  # [1, 4, 9, 16, 25]

# dengan filter
genap = [x for x in range(20) if x % 2 == 0]
print(genap)

# transformasi string
nama = ["andi", "budi", "citra"]
kapital = [n.upper() for n in nama]
print(kapital)

# set comprehension
unik = {x % 3 for x in range(10)}
print(unik)  # {0, 1, 2}

huruf = ["a", "b", "c", "d", "e", "f", "g"]
print(huruf[2:5])    # ["c", "d", "e"]
print(huruf[:3])     # ["a", "b", "c"]
print(huruf[4:])     # ["e", "f", "g"]
print(huruf[::2])    # ["a", "c", "e", "g"]
print(huruf[::-1])   # ["g", "f", "e", "d", "c", "b", "a"]
print(huruf[-3:])    # ["e", "f", "g"]

# slice pada string
s = "Belajar Python"
print(s[0:7])    # Belajar
print(s[::-1])   # nohtyP rajaleB

koordinat = (3, 7)
x, y = koordinat
print(f"x={x}, y={y}")

# swap tanpa variabel bantu
a, b = 1, 2
a, b = b, a
print(a, b)  # 2 1

# tuple dari fungsi
hasil = divmod(17, 5)  # (bagi, sisa)
print(f"17 bagi 5 = {hasil[0]} sisa {hasil[1]}")

# tuple sebagai kunci dict (list tidak bisa)
harga = {(3, 7): "mahal", (1, 2): "murah"}
print(harga[(3, 7)])  # mahal

a = {1, 2, 3, 4, 5}
b = {4, 5, 6, 7, 8}

print(a | b)  # union: semua
print(a & b)  # intersection: sama
print(a - b)  # difference: di A saja
print(a ^ b)  # symmetric: bukan keduanya

# deduplikasi
data = [1, 2, 2, 3, 3, 3, 4]
unik = list(set(data))
print(unik)  # [1, 2, 3, 4]

# keanggotaan cepat
print(3 in a)  # True

stok = {"kopi": 12, "teh": 8}
stok["susu"] = 5
stok["teh"] += 2

# get dengan cadangan
print(stok.get("matcha", 0))   # 0 — tanpa error

# iterasi kunci-nilai
for produk, jumlah in stok.items():
    print(f"{produk}: {jumlah}")

# merge (Python 3.9+)
harga = {"kopi": 18000, "teh": 8000}
gabung = stok | {"diskon": True}
print(gabung)

# hapus
stok.pop("teh")
print("teh" in stok)  # False

# unpack dasar
a, b, c = 1, 2, 3
print(a, b, c)  # 1 2 3

# star menangkap sisanya
first, *tengah, last = [1, 2, 3, 4, 5]
print(first, tengah, last)  # 1 [2, 3, 4] 5

# pack: splat ke fungsi
angka = [10, 20, 30]
print(*angka)  # 10 20 30

# unpack dict
data = {"nama": "Ari", "umur": 17}
for k, v in data.items():
    print(f"{k} = {v}")

def diskon(harga, persen):
    """Hitung nilai diskon dari harga."""
    return harga * persen / 100

def faktorial(n):
    if n <= 1:
        return 1
    return n * faktorial(n - 1)

print(diskon(100000, 20))
print(faktorial(5))
print(help(diskon))

def sapa(nama, sapaan="Halo"):
    return f"{sapaan}, {nama}!"

print(sapa("Ari"))
print(sapa("Budi", "Selamat pagi"))
print(sapa(nama="Citra", sapaan="Oi"))

def jumlah(*angka):
    total = 0
    for n in angka:
        total += n
    return total

print(jumlah(1, 2, 3, 4, 5))  # 15

def profil(**data):
    for k, v in data.items():
        print(f"  {k}: {v}")

profil(nama="Ari", umur=17, kota="Bandung")

angka = [3, 8, 1, 9, 4, 6]

# lambda + sort
pasangan = [("andi", 85), ("budi", 92), ("citra", 78)]
pasangan.sort(key=lambda p: p[1], reverse=True)
print(pasangan)

# map
dobel = list(map(lambda x: x * 2, angka))
print(dobel)

# filter
besar = list(filter(lambda x: x > 5, angka))
print(besar)

# comprehension setara
print([x * 2 for x in angka])
print([x for x in angka if x > 5])

counter = 0  # global

def tambah_local():
    counter = 100  # local — global tidak tersentuh

def tambah_global():
    global counter
    counter += 1

tambah_local()
print(counter)  # 0 — tidak berubah

tambah_global()
tambah_global()
print(counter)  # 2 — global diubah

import math
import random

print(math.sqrt(144))
print(math.pi)
print(random.randint(1, 6))
print(random.choice(["kung", "pao", "chili"]))

# if __name__ == "__main__"
if __name__ == "__main__":
    print("Dijalankan langsung — bukan diimpor.")

$ python -m venv envku
$ source envku/bin/activate      # Mac/Linux
$ envku\Scripts\activate          # Windows

(envku) $ pip install requests
(envku) $ pip list
(envku) $ pip freeze > requirements.txt
(envku) $ deactivate

from datetime import datetime, date, timedelta

sekarang = datetime.now()
print(sekarang)
print(sekarang.strftime("%d/%m/%Y %H:%M"))

# parsing
ulang = datetime.strptime("15/03/2007", "%d/%m/%Y")
print(f"Tahun lahir: {ulang.year}")

# timedelta
besok = date.today() + timedelta(days=1)
print(f"Besok: {besok}")

class Siswa:
    def __init__(self, nama, poin):
        self.nama = nama
        self.poin = poin

    def info(self):
        return f"{self.nama} ({self.poin} poin)"

ari = Siswa("Ari", 10)
budi = Siswa("Budi", 25)
print(ari.info())
print(budi.info())

class Siswa:
    def __init__(self, nama, poin=0):
        self.nama = nama
        self.poin = poin

    def tambah(self, n):
        self.poin += n

    def kurang(self, n):
        self.poin -= n

    def lulus(self):
        return self.poin >= 70

ari = Siswa("Ari")
ari.tambah(50)
ari.tambah(25)
print(ari.poin, ari.lulus())  # 75 True

class Siswa:
    jumlah = 0  # class attribute — dibagi semua

    def __init__(self, nama):
        self.nama = nama
        Siswa.jumlah += 1

    @classmethod
    def dari_string(cls, teks):
        nama = teks.split(",")[0]
        return cls(nama)

    @staticmethod
    def valid(nama):
        return len(nama) >= 2

ari = Siswa("Ari")
budi = Siswa("Budi")
citra = Siswa.dari_string("Citra,17")
print(Siswa.jumlah)          # 3
print(Siswa.valid("A"))     # False

class Pengguna:
    def __init__(self, nama, email):
        self.nama = nama
        self.email = email

    def info(self):
        return f"{self.nama} <{self.email}>"

class Admin(Pengguna):
    def __init__(self, nama, email, level):
        super().__init__(nama, email)
        self.level = level

    def info(self):  # override
        return f"[Admin L{self.level}] {super().info()}"

admin = Admin("Zaky", "ops@site.dev", 5)
print(admin.info())  # [Admin L5] Zaky <ops@site.dev>

class Kucing:
    def bersuara(self): return "meong"

class Anjing:
    def bersuara(self): return "guk guk"

for hewan in [Kucing(), Anjing()]:
    print(hewan.bersuara())

class Uang:
    def __init__(self, jumlah):
        self.jumlah = jumlah
    def __str__(self):
        return f"Rp{self.jumlah:,}"
    def __add__(self, lain):
        return Uang(self.jumlah + lain.jumlah)

print(Uang(15000) + Uang(25000))  # Rp40.000

from abc import ABC, abstractmethod

class Bentuk(ABC):
    @abstractmethod
    def luas(self): pass

class Persegi(Bentuk):
    def __init__(self, sisi):
        self.sisi = sisi
    def luas(self):
        return self.sisi ** 2

print(Persegi(4).luas())  # 16

# dataclass: boilerplate hilang
from dataclasses import dataclass

@dataclass
class Produk:
    nama: str
    harga: int
    stok: int = 0

p = Produk("Kopi", 18000)
print(p)  # Produk(nama='Kopi', harga=18000, stok=0)

import time
import functools

def ukur_waktu(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        mulai = time.perf_counter()
        hasil = func(*args, **kwargs)
        durasi = time.perf_counter() - mulai
        print(f"{func.__name__}: {durasi:.4f}s")
        return hasil
    return wrapper

@ukur_waktu
def hitung_berat(n):
    return sum(range(n))

print(hitung_berat(1_000_000))

def bagi(a, b):
    if b == 0:
        raise ZeroDivisionError("pembagi tidak boleh nol")
    return a / b

try:
    hasil = bagi(10, 2)
except ZeroDivisionError as e:
    print(f"Gagal: {e}")
else:
    print(f"Hasil: {hasil}")
finally:
    print("Selesai.")

# input aman dengan loop
while True:
    try:
        umur = int(input("Umur: "))
        if 1 <= umur <= 120:
            break
        print("Di luar rentang wajar.")
    except ValueError:
        print("Angka saja ya.")

# tulis
with open("catatan.txt", "w") as f:
    f.write("baris pertama\n")
    f.write("baris kedua\n")

# baca per baris
with open("catatan.txt", "r") as f:
    for i, baris in enumerate(f, 1):
        print(f"{i}: {baris.strip()}")

# tambah di akhir
with open("catatan.txt", "a") as f:
    f.write("baris ketiga\n")

import os
print(os.listdir("."))

import json

# Python → JSON → Python
data = {"nama": "Ari", "umur": 17, "hobi": ["coding", "game"]}
teks = json.dumps(data, indent=2)
print(teks)

kembali = json.loads(teks)
print(kembali["hobi"][0])  # coding

# JSON ke berkas
with open("data.json", "w") as f:
    json.dump(data, f)

with open("data.json") as f:
    hasil = json.load(f)
print(hasil["nama"])

import argparse

parser = argparse.ArgumentParser(description="Kalkulator diskon")
parser.add_argument("harga", type=int, help="harga asli")
parser.add_argument("--diskon", type=int, default=10, help="persen diskon")
parser.add_argument("--verbose", action="store_true", help="tampilkan detail")

args = parser.parse_args()
hasil = args.harga - (args.harga * args.diskon // 100)

if args.verbose:
    print(f"Harga: {args.harga}, diskon {args.diskon}%")
print(f"Bayar: {hasil}")

def proses(perintah):
    match perintah:
        case ["tambah", x, y]:
            return x + y
        case ["kurang", x, y]:
            return x - y
        case ["info", nama] if len(nama) > 2:
            return f"Halo {nama}"
        case _:
            return "Tidak dikenal"

print(proses(["tambah", 3, 5]))   # 8
print(proses(["kurang", 10, 4]))  # 6
print(proses(["info", "Ari"]))    # Halo Ari
print(proses(["hapus"]))          # Tidak dikenal

from typing import List

def hitung_diskon(harga: int, persen: float) -> float:
    return harga * (1 - persen / 100)

def cari_maks(data: List[int]) -> int:
    maks: int = data[0]
    for n in data:
        if n > maks:
            maks = n
    return maks

print(hitung_diskon(100000, 20))
print(cari_maks([3, 8, 1, 9, 4]))

# walrus
teks = ""
while (teks := input("Kata (selesai=stop): ")) != "selesai":
    print(f"Panjang: {len(teks)}")