Python 3.15 Yaygın Hataları ve Environment Management Rehberi: ModuleNotFoundError Çözümleri (2026)

Python 3.15 Timeline / Zaman Çizelgesi:

? Python 3.15.0a1: Ekim 2025 (October 2025)
? Python 3.15.0a5: Ocak 2026 (January 2026 - latest alpha)
? Python 3.15.0 Beta: Mayıs 2026 (May 2026 - expected)
? Python 3.15.0 Final: Ekim 2026 (October 2026 - expected)

⚠️ Alpha sürüm: Production'da KULLANMAYIN! (DON'T use in production!)
      

Hata Sıklığı İstatistikleri / Error Frequency Statistics:

? Stack Overflow Python Soruları (2025-2026):

1. ModuleNotFoundError: %28
2. ImportError: %15
3. UnboundLocalError: %12
4. ValueError: %10
5. FileNotFoundError: %8
6. PermissionError: %6
7. AttributeError: %5
8. Diğerleri (Others): %16
      

pip ile Kurulum / Installation with pip:

# Temel kurulum (basic installation)
pip install requests

# Belirli versiyon (specific version)
pip install pandas==2.1.0

# Birden fazla paket (multiple packages)
pip install django flask fastapi

# requirements.txt'ten (from requirements.txt)
pip install -r requirements.txt
      

Environment Kontrolü / Check Environment:

# Hangi Python kullanıyorsunuz? (which Python are you using?)
which python
# veya Windows'ta (or on Windows)
where python

# Hangi pip kullanıyorsunuz?
which pip
# veya Windows'ta
where pip

# Kurulu paketleri listele (list installed packages)
pip list

# Belirli paket var mı kontrol et (check if specific package exists)
pip show requests
      

Python PATH'i Kontrol Et:

# Python'un modül arama yollarını göster (show Python module search paths)
python -c "import sys; print('\n'.join(sys.path))"

# Çıktı örneği (example output):
# /home/alesta/project
# /usr/lib/python3.13
# /usr/local/lib/python3.13/site-packages
      

# ❌ Yanlış (Wrong):
pip install beautifulsoup4
import beautifulsoup4  # Hata! (Error!)

# ✅ Doğru (Correct):
pip install beautifulsoup4
import bs4  # Import adı farklı! (Different import name!)
      

Virtual Environment Olmadan (Without venv):

❌ Proje A: Django 4.2 kullanıyor (uses Django 4.2)
❌ Proje B: Django 5.0 kullanıyor (uses Django 5.0)
❌ Global Python'da sadece 1 versiyon olabilir → CONFLICT! (only 1 version possible)
      

Virtual Environment İle (With venv):

✅ Proje A: Kendi venv'i → Django 4.2
✅ Proje B: Kendi venv'i → Django 5.0
✅ Her proje izole (isolated) → NO CONFLICT!
      

Adım 1: venv Oluştur / Create venv:

# venv oluştur (create venv)
python -m venv myenv

# veya Python 3.13 belirt (or specify Python 3.13)
python3.13 -m venv myenv
      

Adım 2: Aktive Et / Activate:

# Linux/macOS
source myenv/bin/activate

# Windows (cmd)
myenv\Scripts\activate.bat

# Windows (PowerShell)
myenv\Scripts\Activate.ps1

# Aktif mi kontrol et (check if active)
which python  # Linux/macOS
where python  # Windows
# Çıktı (Output): /path/to/myenv/bin/python ✓
      

Adım 3: Paket Kur / Install Packages:

# Paket kur (install package)
pip install django requests pandas

# requirements.txt oluştur (create requirements.txt)
pip freeze > requirements.txt

# requirements.txt'i inceleyebilirsiniz (inspect requirements.txt)
cat requirements.txt
      

Adım 4: Deaktive Et / Deactivate:

# venv'den çık (exit venv)
deactivate
      

venv Özellikleri / venv Features:

✅ Python ile birlikte gelir (comes with Python)
✅ Basit ve hızlı (simple and fast)
✅ Hafif (lightweight)
✅ Sadece Python paketleri (Python packages only)

❌ System dependencies yönetmiyor (doesn't manage system dependencies)
❌ Python versiyonu değiştiremiyor (can't switch Python version easily)

? Kullanım (Usage):
python -m venv venv
source venv/bin/activate
pip install -r requirements.txt
      

conda Özellikleri:

✅ Python + system dependencies (örn: CUDA, C++ libraries)
✅ Python versiyonu değiştirme (switch Python versions)
✅ Data science için ideal (ideal for data science)
✅ conda-forge pakethane (conda-forge repository)

❌ Yavaş (slower than venv/poetry)
❌ Büyük kurulum (large installation ~500MB)
❌ Bazen pip ile çakışma (sometimes conflicts with pip)

? Kullanım:
conda create -n myenv python=3.13
conda activate myenv
conda install pandas numpy scipy
      

poetry Özellikleri:

✅ Modern dependency resolution (çakışmaları önler / prevents conflicts)
✅ pyproject.toml kullanır (uses pyproject.toml)
✅ Lock file (poetry.lock) - reproducible builds
✅ Paket yayınlama (publish to PyPI) kolaylığı

❌ Öğrenme eğrisi (learning curve)
❌ Ekstra kurulum gerekli (requires separate installation)

? Kullanım:
poetry new myproject
cd myproject
poetry add django requests
poetry install
poetry run python app.py
      

pip-tools ile Dependency Resolution:

# pip-tools kur (install pip-tools)
pip install pip-tools

# requirements.in oluştur (create requirements.in)
cat > requirements.in << EOF
django>=4.0
celery
redis
EOF

# Compile et (compile)
pip-compile requirements.in

# Çıktı: requirements.txt (uyumlu versiyonlarla / with compatible versions)
# Kur (install)
pip-sync requirements.txt
      

# poetry otomatik çözüm bulur (poetry finds solution automatically)
poetry add django celery redis

# Conflict varsa gösterir ve alternatif sunar (shows conflict and offers alternatives)
# poetry.lock dosyası oluşturur (creates poetry.lock file)
      

Belirli Versiyonları Zorla / Force Specific Versions:

# requirements.txt
django==4.2.8
celery==5.3.4
redis==5.0.1
requests==2.31.0

# Exact version kullan (use exact versions)
pip install -r requirements.txt
      

# Örnek: requests yerine httpx (example: httpx instead of requests)
pip install httpx  # Modern, async-capable alternative

# Örnek: pandas yerine polars (faster alternative)
pip install polars
      

# ✅ Her proje için venv (venv for each project)
cd myproject
python -m venv .venv
source .venv/bin/activate  # Linux/macOS
.venv\Scripts\activate     # Windows

# .gitignore'a ekle (add to .gitignore)
echo ".venv/" >> .gitignore
      

# ❌ Kötü (Bad):
django
requests

# ✅ İyi (Good):
django==4.2.8
requests==2.31.0

# ✅ Daha İyi (Better - version range):
django>=4.2,<5.0
requests>=2.30,<3.0
      

# requirements.txt oluştur (create)
pip freeze > requirements.txt

# Yükle (install)
pip install -r requirements.txt

# Güncelle (update)
pip install --upgrade -r requirements.txt
pip freeze > requirements.txt
      

pyproject.toml Örneği:

[tool.poetry]
name = "alesta-web-app"
version = "1.0.0"
description = "Alesta Web Python Projesi"

[tool.poetry.dependencies]
python = "^3.13"
django = "^4.2"
celery = "^5.3"

[tool.poetry.dev-dependencies]
pytest = "^7.4"
black = "^23.0"
      

Type Hints Örneği:

# Type hints ile daha güvenli kod (safer code with type hints)
def calculate_price(price: float, tax_rate: float = 0.18) -> float:
    """
    Fiyat hesapla (calculate price with tax)

    Args:
        price: Ürün fiyatı (product price)
        tax_rate: Vergi oranı (tax rate), varsayılan 0.18

    Returns:
        Vergili toplam fiyat (total price with tax)
    """
    return price * (1 + tax_rate)

# Kullanım (usage)
total = calculate_price(100.0)  # 118.0
print(f"Alesta Web ürün fiyatı: {total} TL")
      

GitHub Actions Örneği:

# .github/workflows/python-tests.yml
name: Python Tests
on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-python@v4
        with:
          python-version: '3.13'
      - run: pip install -r requirements.txt
      - run: pytest