python lambda examples

Example 1: what is lambda in python

Lamda is just one line anonymous function
Useful when writing function inside function
it can take multiple arguments but computes only one expression

Syntax:
   x = lambda arguments : expression

Example 2: lambda function in python

In Python, an anonymous function is a function that is defined without a name.

While normal functions are defined using the def keyword in Python, 
anonymous functions are defined using the lambda keyword.

Hence, anonymous functions are also called lambda functions.

# syntax of Lambda function
lambda arguments: expression

# Program to show the use of lambda functions
double = lambda x: x * 2

print(double(5))

# examples
my_list = range(101)

print(list(map(lambda item: item**2, my_list)))
print(list(filter(lambda item: item % 2 == 1, my_list)))
print(list(map(lambda item: item**2, my_list)))

a = [(0, 2), (4, 3), (9, 9), (10, -1)]

a.sort(key=lambda x: x[1])

print(a)

# docs lambda function
# the lambda function can be used as a function inside a function like the following


def make_incrementor(n):
    return lambda x: x + n


f = make_incrementor(12)
print(f(3))
print(f(13))

# you can use lambda as a key for sort or anything else
pairs = [(1, "one"), (2, "two"), (3, "three"), (4, "four")]
# what if you wanna sort the list by the second argument
pairs.sort(key=lambda x: x[1])
print(pairs)

Example 3: lambda python

def sumn(n):
  return lambda a: a + n
sum5 = sumn(5)
sum5(3) ## 8

Example 4: lambda function in python

>>> def identity(x):
...     return x

These two functions do the same thing

>>> lambda x: x