Python Tutorial (3): Control Flow: Percabangan dan Perulangan

score = 85
 
if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
else:
    grade = "D"
 
print(f"Grade: {grade}")   # Grade: B

status = "dewasa" if age >= 18 else "anak-anak"
result = x if x > 0 else -x   # absolute value

items = [1, 2, 3]
 
if items:           # True jika list tidak kosong
    print("Ada item")
 
name = ""
if not name:        # True jika string kosong
    name = "Anonymous"

# Iterasi list
fruits = ["apel", "jeruk", "mangga"]
for fruit in fruits:
    print(fruit)
 
# range(start, stop, step)
for i in range(5):          # 0, 1, 2, 3, 4
    print(i)
 
for i in range(2, 10, 2):  # 2, 4, 6, 8
    print(i)
 
# enumerate: index + value
for i, fruit in enumerate(fruits):
    print(f"{i}: {fruit}")
 
# zip: iterasi paralel
names = ["Alice", "Bob"]
scores = [90, 85]
for name, score in zip(names, scores):
    print(f"{name}: {score}")
 
# Iterasi dictionary
config = {"host": "localhost", "port": 8080}
for key, value in config.items():
    print(f"{key} = {value}")
 
# Iterasi string
for char in "Python":
    print(char)

count = 0
while count < 5:
    print(count)
    count += 1
 
# Input loop
while True:
    answer = input("Ketik 'quit' untuk keluar: ")
    if answer == "quit":
        break

# break: keluar dari loop
for n in range(100):
    if n > 10:
        break
    print(n)
 
# continue: skip iterasi saat ini
for n in range(10):
    if n % 2 == 0:
        continue    # skip genap
    print(n)        # hanya ganjil
 
# for...else: else dieksekusi jika loop selesai tanpa break
for n in range(2, 100):
    for i in range(2, int(n**0.5) + 1):
        if n % i == 0:
            break
    else:
        print(f"{n} adalah bilangan prima")

# List comprehension
squares = [x**2 for x in range(10)]
evens = [x for x in range(20) if x % 2 == 0]
pairs = [(x, y) for x in range(3) for y in range(3)]
 
# Dict comprehension
word_lengths = {word: len(word) for word in ["hello", "world", "python"]}
# {'hello': 5, 'world': 5, 'python': 6}
 
# Set comprehension
unique_lengths = {len(word) for word in ["hi", "hello", "hey"]}
# {2, 5, 3}
 
# Generator expression (lazy, hemat memory)
total = sum(x**2 for x in range(1000000))

# Terlalu kompleks untuk comprehension, pakai loop
results = []
for item in data:
    processed = transform(item)
    if validate(processed):
        results.append(processed)

command = input("Command: ")
 
match command.split():
    case ["quit"]:
        print("Exiting...")
    case ["hello", name]:
        print(f"Hello, {name}!")
    case ["add", *numbers]:
        total = sum(int(n) for n in numbers)
        print(f"Sum: {total}")
    case _:
        print("Unknown command")

# Pattern matching dengan tipe
def process(value):
    match value:
        case int(n) if n > 0:
            return f"Positive int: {n}"
        case str(s) if len(s) > 0:
            return f"Non-empty string: {s}"
        case [first, *rest]:
            return f"List starting with {first}"
        case {"name": name, "age": age}:
            return f"{name} is {age}"
        case _:
            return "Unknown"

from itertools import chain, product, groupby
 
# Chain: gabung multiple iterables
combined = list(chain([1, 2], [3, 4], [5]))
# [1, 2, 3, 4, 5]
 
# Product: cartesian product
for size, color in product(["S", "M", "L"], ["red", "blue"]):
    print(f"{size}-{color}")
 
# Reversed
for item in reversed(fruits):
    print(item)
 
# Sorted dengan key
students = [("Alice", 90), ("Bob", 85), ("Charlie", 92)]
for name, score in sorted(students, key=lambda x: x[1], reverse=True):
    print(f"{name}: {score}")

# Tanpa walrus
line = input()
while line != "quit":
    print(f"You said: {line}")
    line = input()
 
# Dengan walrus
while (line := input()) != "quit":
    print(f"You said: {line}")
 
# Dalam comprehension
results = [y for x in data if (y := expensive_func(x)) > threshold]