Lambda function in Python

Elderly Beginner · October 31, 2019

I skipped lambda function several times when I was reading and learning Python. You have:

  1. Regular def function e.g.:
def plus(a, b):
	return(a + b)
  1. Comprehensive lists e.g.:
power = [x * x for x in range(10)]

So, what is lambda for?
Well, I still don’t know, but finally I read about it and I believe I have grasped how it works.

I’m telling myself that:

  1. I’m assigning function to variable
  2. When I call lambda function/variable with an argument, this argument makes input before ‘:’ and function give output after ‘:’

Looks like it works in my head.

>>> import math
>>> PI = math.pi
>>> sin_lambda = lambda x: math.sin(x*PI/180)
>>> cos_lambda = lambda y: math.cos(y*PI/180)
>>> type(sin_lambda)
<class 'function'>
>>> sin_lambda(0)
0.0
>>> sin_lambda(90)
1.0
>>> sin_lambda(30)
0.49999999999999994

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