Lambda function = A small anonymous function for a one time use (throw away function) They take any number of arguments, but have only 1 expression Helps keep the namespace clean and is useful with higher-order functions : 'sort()', 'map()', 'filter()', 'reduce()' lambda parameters: expression
Ex:
double = lambda x : x * 2
add = lambda x ,y : x + y
max_value = lambda x, y : x if x > y else y
min_value = lambda x, y : x if x < y else y
full_name = lambda first, last: first + " "+ last
is_even = lambda x : "odd" if x % 2 == 0 else "even"
age_check = lambda age : "Kick-in "if age >= 18 else "Kick-out"
print(double(2))
print(add(2, 3))
print(max_value(6, 5))
print(max_value(4, 5))
print(age_check(12))
print(is_even(4))
- map(function, collection) = Applies a given function to all items in a collection
ex:
celsius_temps = [0.0, 10.0, 20.0, 30.0, 40.0, 50.0] fahrenheit_temps = list(map(lambda temp: (temp * 9/5) + 32, celsius_temps))
print(fahrenheit_temps)
- filter(condition, collection) = return all elements that pass a condition
ex:
grades = [91, 32, 83, 54, 72, 63, 47]
passing_grades = filter(lambda grade : grade >= 60 , grades)
for grade in passing_grades:
print(grade)
- reduce(function, collection) = Reduces elements in a collection to a single value For loop is better in most cases Reduce is better for a functional approach + readability
ex:
from functools import reduce
prices = [19.99, 1.00, 5.75, 12.99, 10.99]
total = reduce(lambda x, y: x + y, prices)
print(f"${total}")
- SORTING IN PYTHON .sort() or sorted() Lists[], Tuples(), Dictionaries{"":""}, Objects
ex:
--------- LISTS ---------
fruits = ["banana", "orange", "apple", "coconut"]
fruits.sort()
fruits.sort(reverse=True)
print(fruits)
--------- TUPLES ---------
fruits = ("banana", "orange", "apple", "coconut")
fruits = tuple(sorted(fruits))
fruits = tuple(sorted(fruits, reverse=True))
print(fruits)
--------- DICTIONARIES ---------
fruits = { "banana": 105,
"apple": 72,
"orange": 73,
"coconut": 354 }
fruits = dict(sorted(fruits.items()))
fruits = dict(sorted(fruits.items(), key=lambda item: item[0], reverse=True))
fruits = dict(sorted(fruits.items(), key=lambda item: item[1])) fruits = dict(sorted(fruits.items(), key=lambda item: item[1], reverse=True))
print(fruits)
--------- OBJECTS ---------
class Fruit:
def __init__(self, name, calories):
self.name = name
self.calories = calories
def __repr__(self):`
`return f"{self.name}: {self.calories}"
fruits = [Fruit("banana", 105),
Fruit("apple", 72),
Fruit("orange", 73),
Fruit("coconut", 354)]
fruits = sorted(fruits, key=lambda fruit: fruit.name)
fruits = sorted(fruits, key=lambda fruit: fruit.name, reverse=True)
fruits = sorted(fruits, key=lambda fruit: fruit.calories)
fruits = sorted(fruits, key=lambda fruit: fruit.calories, reverse=True)
print(fruits)
ref:[[Functions]]