Python Iterables Part 3: Analysis Tools and Techniques

Understanding len() with Different Types

# Lists - counts elements
colors = ['red', 'green', 'blue']
print(f"Number of colors: {len(colors)}")

# Strings - counts characters
message = "Hello, Python!"
print(f"Message length: {len(message)}")

# Dictionaries - counts key-value pairs
user = {
    'name': 'Alice',
    'age': 30,
    'city': 'New York'
}
print(f"Number of user attributes: {len(user)}")

# Practical Example: Validating Input
def validate_username(username):
    """
    Validates a username based on length criteria:
    - Must be between 3 and 20 characters
    - Cannot contain spaces
    """
    if len(username) < 3:
        return "Username too short (minimum 3 characters)"
    if len(username) > 20:
        return "Username too long (maximum 20 characters)"
    if len(username.split()) > 1:
        return "Username cannot contain spaces"
    return "Username is valid"

# Testing username validation
usernames = ['al', 'bob', 'charlie brown', 'thisisaverylongusername123']
for username in usernames:
    print(f"'{username}': {validate_username(username)}")
                

Basic Usage and Advanced Techniques

# Simple number comparisons
numbers = [23, 45, 12, 67, 89, 34]
print(f"Highest number: {max(numbers)}")
print(f"Lowest number: {min(numbers)}")

# Working with strings
names = ['Alice', 'bob', 'Charlie', 'david']
# Case-sensitive comparison
print(f"First alphabetically (case-sensitive): {min(names)}")
# Case-insensitive comparison
print(f"First alphabetically (case-insensitive): {min(names, key=str.lower)}")

# Complex object comparison
class Student:
    def __init__(self, name, grade, attendance):
        self.name = name
        self.grade = grade
        self.attendance = attendance
    
    def __repr__(self):
        return f"{self.name} (Grade: {self.grade}, Attendance: {self.attendance}%)"

students = [
    Student('Alice', 95, 98),
    Student('Bob', 87, 92),
    Student('Charlie', 92, 85)
]

# Finding top performer based on grade
top_grade = max(students, key=lambda s: s.grade)
print(f"\nHighest grade: {top_grade}")

# Finding top performer based on combined metrics
def performance_score(student):
    """Calculate overall performance score"""
    return (student.grade * 0.7) + (student.attendance * 0.3)

top_performer = max(students, key=performance_score)
print(f"Best overall performer: {top_performer}")
                

Practical Application: Market Analysis

# Stock market data analysis
stock_data = [
    {'symbol': 'AAPL', 'price': 150.25, 'volume': 1000000},
    {'symbol': 'GOOGL', 'price': 2750.75, 'volume': 500000},
    {'symbol': 'MSFT', 'price': 290.50, 'volume': 750000}
]

# Finding highest and lowest priced stocks
highest_price = max(stock_data, key=lambda x: x['price'])
lowest_price = min(stock_data, key=lambda x: x['price'])

print("\nStock Analysis:")
print(f"Highest priced stock: {highest_price['symbol']} at ${highest_price['price']}")
print(f"Lowest priced stock: {lowest_price['symbol']} at ${lowest_price['price']}")

# Finding stock with highest market value
def market_value(stock):
    return stock['price'] * stock['volume']

largest_cap = max(stock_data, key=market_value)
print(f"Largest market cap: {largest_cap['symbol']}")
                

Advanced Summation Techniques

# Basic summation
expenses = [123.45, 234.56, 345.67, 456.78]
total = sum(expenses)
print(f"Total expenses: ${total:.2f}")

# Calculating average with sum()
average = sum(expenses) / len(expenses)
print(f"Average expense: ${average:.2f}")

# More complex calculations
sales_data = [
    {'product': 'Widget A', 'units': 100, 'price': 50},
    {'product': 'Widget B', 'units': 50, 'price': 100},
    {'product': 'Widget C', 'units': 75, 'price': 75}
]

# Calculate total revenue
total_revenue = sum(item['units'] * item['price'] for item in sales_data)
print(f"\nTotal revenue: ${total_revenue:,.2f}")

# Calculate total units sold by product category
units_by_category = {
    'Widget A': [100, 150, 200],
    'Widget B': [50, 75, 60],
    'Widget C': [75, 80, 85]
}

category_totals = {
    category: sum(units)
    for category, units in units_by_category.items()
}

print("\nTotal units sold by category:")
for category, total in category_totals.items():
    print(f"{category}: {total} units")
                

Validation and Checking

# Basic usage
numbers = [2, 4, 6, 8, 9]
has_odd = any(num % 2 == 1 for num in numbers)
all_even = all(num % 2 == 0 for num in numbers)

print(f"Contains odd numbers: {has_odd}")
print(f"All numbers are even: {all_even}")

# Practical Example: Form Validation
class FormValidator:
    def __init__(self, data):
        self.data = data
    
    def validate_required_fields(self, required):
        """Check if all required fields are present and non-empty"""
        return all(
            field in self.data and self.data[field].strip()
            for field in required
        )
    
    def validate_numeric_fields(self, numeric_fields):
        """Check if specified fields contain valid numbers"""
        return all(
            field in self.data and str(self.data[field]).replace('.', '').isdigit()
            for field in numeric_fields
        )

# Testing form validation
form_data = {
    'name': 'John Doe',
    'age': '30',
    'email': 'john@example.com',
    'phone': ''
}

validator = FormValidator(form_data)
required_fields = ['name', 'email', 'phone']
numeric_fields = ['age']

print("\nForm Validation:")
print(f"All required fields present: {validator.validate_required_fields(required_fields)}")
print(f"All numeric fields valid: {validator.validate_numeric_fields(numeric_fields)}")