🚀 *Gen AI Engineer Telugu (Production Focused)* Lambda Functions in Python
Lambda functions are small, anonymous functions defined using the lambda keyword. They can take any number of arguments but can only have one expression.
Basic Syntax
python
lambda arguments: expression
Simple Examples
1. Basic Lambda Function
python
# Regular function
def add(x, y):
return x + y
# Equivalent lambda function
add_lambda = lambda x, y: x + y
print(add(5, 3)) # Output: 8
print(add_lambda(5, 3)) # Output: 8
2. Single Argument Lambda
python
# Double a number double = lambda x: x * 2 print(double(7)) # Output: 14 # Square a number square = lambda x: x ** 2 print(square(4)) # Output: 16
Lambda with Built-in Functions
3. Using with map()
python
numbers = [1, 2, 3, 4, 5] # Double each number using map + lambda doubled = list(map(lambda x: x * 2, numbers)) print(doubled) # Output: [2, 4, 6, 8, 10]
4. Using with filter()
python
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] # Filter even numbers evens = list(filter(lambda x: x % 2 == 0, numbers)) print(evens) # Output: [2, 4, 6, 8, 10] # Filter numbers greater than 5 greater_than_5 = list(filter(lambda x: x > 5, numbers)) print(greater_than_5) # Output: [6, 7, 8, 9, 10]
5. Using with sorted()
python
# Sort by length of words words = ["apple", "banana", "cherry", "date"] sorted_by_length = sorted(words, key=lambda x: len(x)) print(sorted_by_length) # Output: ['date', 'apple', 'banana', 'cherry'] # Sort by last character sorted_by_last_char = sorted(words, key=lambda x: x[-1]) print(sorted_by_last_char) # Output: ['banana', 'apple', 'date', 'cherry']
Practical Examples
6. Simple Calculator Operations
python
operations = {
'add': lambda x, y: x + y,
'subtract': lambda x, y: x - y,
'multiply': lambda x, y: x * y,
'divide': lambda x, y: x / y if y != 0 else "Cannot divide by zero"
}
print(operations['add'](10, 5)) # Output: 15
print(operations['multiply'](4, 6)) # Output: 24
print(operations['divide'](10, 2)) # Output: 5.0
7. Conditional Logic in Lambda
python
# Check if number is positive is_positive = lambda x: True if x > 0 else False print(is_positive(5)) # Output: True print(is_positive(-3)) # Output: False # Grade classifier grade = lambda score: "Pass" if score >= 50 else "Fail" print(grade(75)) # Output: Pass print(grade(45)) # Output: Fail
8. Multiple Arguments
python
# Calculate area of rectangle
area = lambda length, width: length * width
print(area(5, 10)) # Output: 50
# String formatting
greet = lambda name, age: f"Hello {name}, you are {age} years old!"
print(greet("Alice", 25)) # Output: Hello Alice, you are 25 years old!
Advanced Examples
9. Immediately Invoked Lambda
python
# Lambda function called immediately
result = (lambda x, y: x ** y)(2, 3)
print(result) # Output: 8
# Another example
message = (lambda name: f"Welcome, {name}!")("Bob")
print(message) # Output: Welcome, Bob!
10. Lambda in List Comprehensions
python
# Create a list of functions
functions = [lambda x, n=i: x + n for i in range(5)]
for i, func in enumerate(functions):
print(f"func({10}, n={i}) = {func(10)}")
11. Using with reduce()
python
from functools import reduce numbers = [1, 2, 3, 4, 5] # Calculate product using reduce + lambda product = reduce(lambda x, y: x * y, numbers) print(product) # Output: 120 (1*2*3*4*5) # Find maximum number max_num = reduce(lambda x, y: x if x > y else y, numbers) print(max_num) # Output: 5
When to Use Lambda Functions
Good for:
- Simple, one-line operations
- Functions used only once
- As arguments to higher-order functions (
map,filter,sorted, etc.)
Not good for:
- Complex logic (use regular
deffunctions) - Functions that need documentation strings
- Functions with multiple statements
Key Points to Remember
- Anonymous: Lambda functions don’t have names (unless assigned to a variable)
- Single Expression: Can only contain one expression
- No Statements: Cannot include statements like
return,pass,assert, etc. - Implicit Return: The expression is automatically returned
Lambda functions make your code more concise and readable when used appropriately for simple operations!
