Python Kodları

s = "Python"
# 1) Dilim (en kısa)
print(s[::-1])          # 'nohtyP'

# 2) Döngü
t = ""
for c in s:
    t = c + t
print(t)                # 'nohtyP'

# 3) join + reversed
print(''.join(reversed(s)))  # 'nohtyP'

def is_palindrome(s: str) -> bool:
    s = s.lower().replace(" ", "")
    return s == s[::-1]

print(is_palindrome("kek"))         # True
print(is_palindrome("A man a plan a canal Panama"))  # True
print(is_palindrome("python"))      # False

def ebob(a: int, b: int) -> int:
    while b:
        a, b = b, a % b
    return a

# math modülü ile:
import math
print(math.gcd(48, 18))  # 6
print(ebob(48, 18))      # 6

# Üç sayının EBOB'u:
print(math.gcd(math.gcd(12, 18), 24))  # 6

def uniq(seq):
    seen = set()
    out = []
    for x in seq:
        if x not in seen:
            seen.add(x)
            out.append(x)
    return out

print(uniq([1, 3, 2, 3, 1, 4]))  # [1, 3, 2, 4]

def binary_search(arr, target):
    lo, hi = 0, len(arr) - 1
    while lo <= hi:
        mid = (lo + hi) // 2
        if arr[mid] == target:
            return mid
        if arr[mid] < target:
            lo = mid + 1
        else:
            hi = mid - 1
    return -1

print(binary_search([1, 3, 5, 7, 9, 11], 7))  # 3

def quick_sort(arr):
    if len(arr) <= 1:
        return arr
    pivot = arr[len(arr) // 2]
    left   = [x for x in arr if x < pivot]
    middle = [x for x in arr if x == pivot]
    right  = [x for x in arr if x > pivot]
    return quick_sort(left) + middle + quick_sort(right)

print(quick_sort([3, 6, 8, 10, 1, 2, 1, 9, 5]))  # [1, 1, 2, 3, 5, 6, 8, 9, 10]

from functools import lru_cache

@lru_cache(maxsize=None)
def fib(n: int) -> int:
    if n < 2:
        return n
    return fib(n - 1) + fib(n - 2)

# İlk 10 sayı:
print([fib(i) for i in range(10)])
# [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

def two_sum(nums, target):
    seen = {}
    for i, x in enumerate(nums):
        kalan = target - x
        if kalan in seen:
            return [seen[kalan], i]
        seen[x] = i
    return []

print(two_sum([2, 7, 11, 15], 9))  # [0, 1]

class Stack:
    def __init__(self):
        self._data = []

    def push(self, x):  self._data.append(x)
    def pop(self):      return self._data.pop() if self._data else None
    def peek(self):     return self._data[-1] if self._data else None
    def is_empty(self): return not self._data

s = Stack()
s.push(1); s.push(2); s.push(3)
print(s.pop(), s.pop(), s.pop())  # 3 2 1
print(s.is_empty())              # True

from collections import deque

class Queue:
    def __init__(self):
        self._data = deque()

    def enqueue(self, x): self._data.append(x)
    def dequeue(self):    return self._data.popleft() if self._data else None
    def is_empty(self):   return not self._data

q = Queue()
q.enqueue('a'); q.enqueue('b'); q.enqueue('c')
print(q.dequeue(), q.dequeue(), q.dequeue())  # a b c

class Node:
    def __init__(self, val, nxt=None):
        self.val, self.next = val, nxt

def to_list(head):
    out, cur = [], head
    while cur:
        out.append(cur.val); cur = cur.next
    return out

# 1 -> 2 -> 3 -> None
head = Node(1, Node(2, Node(3)))
print(to_list(head))  # [1, 2, 3]

# Yazma
with open("notlar.txt", "w", encoding="utf-8") as f:
    f.write("Merhaba\nDünya\n")

# Satır satır okuma
with open("notlar.txt", "r", encoding="utf-8") as f:
    for line in f:
        print(line.rstrip())

import json

data = {
    "ad": "Ali",
    "yas": 28,
    "yetenekler": ["Python", "SQL", "Docker"]
}

# JSON string:
s = json.dumps(data, ensure_ascii=False, indent=2)
print(s)

# JSON string → dict:
parsed = json.loads(s)
print(parsed["ad"])

import csv

# Çok satırlı string (örnek veri)
csv_text = """ad,yas,sehir
Ali,28,İstanbul
Ayşe,32,Ankara
Mehmet,25,İzmir"""

# DictReader ile oku:
from io import StringIO
reader = csv.DictReader(StringIO(csv_text))
for row in reader:
    print(row)

from urllib.parse import urlparse, parse_qs, urlencode

url = "https://api.example.com/search?q=python&page=2"
p = urlparse(url)
print("Host:", p.netloc)
print("Path:", p.path)
print("Query:", parse_qs(p.query))
# {'q': ['python'], 'page': ['2']}

# Yeni URL oluştur:
params = urlencode({"q": "django", "page": 1})
print(f"{p.scheme}://{p.netloc}{p.path}?{params}")

import re

EMAIL_RE = re.compile(r"^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$")

def is_valid_email(s: str) -> bool:
    return bool(EMAIL_RE.match(s))

print(is_valid_email("ali@test.com"))   # True
print(is_valid_email("ali.test@com"))  # False

import time
from functools import wraps

def timer(fn):
    @wraps(fn)
    def wrapper(*args, **kwargs):
        t0 = time.perf_counter()
        out = fn(*args, **kwargs)
        ms = (time.perf_counter() - t0) * 1000
        print(f'{fn.__name__} {ms:.2f} ms')
        return out
    return wrapper

@timer
def yavas():
    sum(range(1_000_00))

yavas()  # 'yavas ~1.5 ms'

from dataclasses import dataclass, field
from typing import List

@dataclass
class Ogrenci:
    ad: str
    yas: int
    notlar: List[int] = field(default_factory=list)

    def ortalama(self) -> float:
        return sum(self.notlar) / len(self.notlar) if self.notlar else 0.0

o = Ogrenci("Ali", 20, [80, 90, 75])
print(o)                # Ogrenci(ad='Ali', yas=20, notlar=[80, 90, 75])
print(o.ortalama())     # 81.6666...

import time
from contextlib import contextmanager

@contextmanager
def zamanlayici(label="block"):
    t0 = time.perf_counter()
    try:
        yield
    finally:
        ms = (time.perf_counter() - t0) * 1000
        print(f'{label}: {ms:.2f} ms')

with zamanlayici("islem"):
    sum(range(100_000))