Python Tutorials · Python Functions

Python Lambda

Learn all about Python Lambda in this comprehensive tutorial.

5 min read beginner

Python Decorators

Python Recursion

•A lambda function is a small anonymous function.
•The expression is executed and the result is returned:
•The power of lambda is better shown when you use them as an anonymous function inside another function.
•Lambda functions are commonly used with built-in functions like map(), filter(), and sorted().

Lambda Functions

A lambda function is a small anonymous function.

A lambda function can take any number of arguments, but can only have one expression.

Syntax

The expression is executed and the result is returned:

python

val_1 = lambda a : a + 10print(val_1(5))

Lambda functions can take any number of arguments:

python

val_1 = lambda a, b : a * bprint(val_1(5, 6))

python

val_1 = lambda a, b, c : a + b + cprint(val_1(5, 6, 
  2))

Why Use Lambda Functions?

The power of lambda is better shown when you use them as an anonymous function inside another function.

Say you have a function definition that takes one argument, and that argument will be multiplied with an unknown number:

python

def myfunc(n):
  return lambda a : a * n

Use that function definition to make a function that always doubles the number you send in:

python

def myfunc(n):
  return lambda a : a * n

  mydoubler = myfunc(2)
print(mydoubler(11))

Or, use the same function definition to make a function that always triples the number you send in:

python

def myfunc(n):
  return lambda a : a * n

  mytripler = myfunc(3)
print(mytripler(11))

Or, use the same function definition to make both functions, in the same program:

python

def myfunc(n):
  return lambda a : a * n

  mydoubler = myfunc(2)mytripler = myfunc(3)
print(mydoubler(11))print(mytripler(11))

Note: Use lambda functions when an anonymous function is required for a short period of time.

Lambda with Built-in Functions

Lambda functions are commonly used with built-in functions like map(), filter(), and sorted().

The map() function applies a function to every item in an iterable:

python

numbers = [1, 2, 3, 4, 5]
doubled = list(map(lambda val_1: val_1 * 2, numbers))
print(doubled)

The filter() function creates a list of items for which a function returns True:

python

numbers = [1, 2, 3, 4, 5, 6, 7, 8]
odd_numbers = list(filter(lambda val_1: val_1 % 2 != 0, numbers))
print(odd_numbers)

The sorted() function can use a lambda as a key for custom sorting:

python

students = [("Emil", 25), ("Tobias", 22), ("Linus", 28)]
sorted_students = sorted(students, key=lambda val_1: val_1[1])
print(sorted_students)

python

words = ["apple", "pie", "banana", "cherry"]
sorted_words = sorted(words, key=lambda val_1: len(val_1))
print(sorted_words)

Module quiz

2 questions

Which of the following is true about Python Lambda?

It is strictly typedIt is evaluated at runtimeIt requires explicit memory managementIt is deprecated

What is the most common pitfall when working with Python Lambda?

SyntaxErrorIndentationErrorNameErrorTypeError

Answer all questions to submit.

Python Decorators

Python Recursion

Python Lambda

AI Summary

Lambda Functions

Syntax

Why Use Lambda Functions?

Lambda with Built-in Functions

Module quiz