Modules & Packages

# mathutils.py — a reusable math utilities module

PI = 3.14159265358979

def circle_area(r):
    """Return area of a circle."""
    return PI * r ** 2

def circle_circumference(r):
    return 2 * PI * r

def is_prime(n):
    """Return True if n is prime."""
    if n < 2: return False
    return all(n % i != 0 for i in range(2, int(n**.5)+1))

# __name__ guard: runs only when executed directly, not when imported
if __name__ == "__main__":
    print("Testing mathutils...")
    print(circle_area(5))    # 78.539...
    print(is_prime(17))       # True

# Style 1: import the whole module (namespace preserved)
import mathutils
print(mathutils.circle_area(3))   # 28.274...
print(mathutils.PI)                # 3.14159...

# Style 2: import specific names
from mathutils import is_prime, PI
print(is_prime(13))   # True — no mathutils. prefix needed

# Style 3: alias (useful for long names)
import mathutils as mu
print(mu.circle_area(7))

# Style 4: from ... import * (generally avoid — pollutes namespace)
# from mathutils import *

# ── Standard library imports ──────────────────
import math
print(math.sqrt(144))     # 12.0
print(math.factorial(10))  # 3628800

import random
print(random.choice(["Ali", "Sara", "Zara"]))
print(random.randint(1, 100))

from datetime import datetime, timedelta
now = datetime.now()
print(now.strftime("%d %B %Y"))
tomorrow = now + timedelta(days=1)

# __init__.py — package initialisation
# Import key names so users can write: from bwb_toolkit import validate_email
from .validators import validate_email, validate_age
from .formatters import format_currency, format_date

__version__ = "1.0.0"
__author__  = "BitWithBite"

# __all__ controls what 'from package import *' exports
__all__ = ["validate_email", "validate_age", "format_currency"]

# bwb_toolkit/validators.py
import re

def validate_email(email):
    """Return True if email is valid format."""
    pattern = re.compile(r'^[\w.-]+@[\w.-]+\.\w{2,}$')
    return bool(pattern.match(email))

def validate_age(age):
    """Return True if age is 5–120."""
    return isinstance(age, int) and 5 <= age <= 120


# main.py — importing from the package
from bwb_toolkit import validate_email   # from __init__
from bwb_toolkit.validators import validate_age  # direct submodule
from bwb_toolkit.data.csv_handler import load_csv  # nested subpackage

print(validate_email("ali@bwb.com"))   # True
print(validate_age(200))               # False

# ── Create a virtual environment ─────────────
python -m venv venv              # creates venv/ folder

# ── Activate it ──────────────────────────────
# Windows:
venv\Scripts\activate

# macOS/Linux:
source venv/bin/activate

# ── Install packages ─────────────────────────
pip install requests             # HTTP library
pip install pandas               # data analysis
pip install flask                # web framework
pip install python-dotenv        # .env file support

# ── Save dependencies ─────────────────────────
pip freeze > requirements.txt    # snapshot all installed packages

# ── Install from requirements.txt ────────────
pip install -r requirements.txt  # used by teammates or on server

# ── Useful pip commands ───────────────────────
pip list                         # show installed packages
pip show requests                # details about a package
pip install --upgrade pip        # upgrade pip itself
pip uninstall flask              # remove a package

# ── Deactivate ────────────────────────────────
deactivate

from collections import Counter, defaultdict
from functools import lru_cache
from itertools import combinations
import re, os

# Counter — count occurrences in one line
words   = "python is easy and python is fun".split()
counts  = Counter(words)
print(counts.most_common(3))   # [('python', 2), ('is', 2), ...]

# defaultdict — no KeyError on missing keys
groups  = defaultdict(list)
students= [("A", "Ali"), ("B", "Sara"), ("A", "Zara")]
for grade, name in students:
    groups[grade].append(name)   # no .setdefault() needed!
print(dict(groups))              # {'A': ['Ali', 'Zara'], 'B': ['Sara']}

# lru_cache — memoize expensive functions
@lru_cache(maxsize=128)
def fib(n):
    if n <= 1: return n
    return fib(n-1) + fib(n-2)
print(fib(50))   # 12586269025 — instant with caching

# re — regex
text = "Call us at 0300-1234567 or 042-3456789"
nums = re.findall(r'\d[\d-]+', text)
print(nums)      # ['0300-1234567', '042-3456789']

# os — environment and paths
print(os.getcwd())
print(os.getenv("HOME", "not set"))

# combinations
teams = list(combinations(["Ali","Sara","Zara","Omar"], 2))
print(teams)  # all 6 pairs