Lambda in Python

Python Lambda Desmistification — #PurePythonSeries — Episode #00

This post attempts to demystify Lambda in Python.

Simply put, a lambda function is just like any normal python function, except that it has no name when defining it, and it is contained in one line of code. A lambda function evaluates an expression for a given argument. You give the function a value (argument) and then provide the operation (expression) — From TowardsDatascience.com.

LAMBDA

How To Get A Lambda Expression just from times2 function?

Here is the original function:

def times2(var):
  return var*2

The times2 function can be written in one line:

Rewriting it in one line:

def times2(var):return var*2

Now, get rid of the def keyword:

times2(var):return var*2

Now, to get a lambda expression just get rid of the name of the function (typing lambda in its place — because lambda is an anonymous function);

lambda(var):return var*2

And get rid of the parentheses adding space in front (cleaning the code:);

lambda var:return var*2

And finally, get rid of return word (its function is assumed by the colon ), like this :)

lambda var:var*2

It Reads: lambda takes var and returns var*2.

Just in one line. Simple Like That! Awesome!

This is not usual for lambda, but it is a feasible use (saving lambda times2 to var t2):

t2 = lambda var:var*2

t2(5)

10

Now use Map plus Lambda together:

# Using Map function plus Lambda function (what it is build for!):

seq = [1,2,3,4,5]
map(lambda var:var*2, seq)

<map at 0x7f0640b37b38>

# Casting Map to a List:

list(map(lambda var:var*2, seq))

[2, 4, 6, 8, 10]

Complete code:)

seq = [1,2,3,4,5]
print(list(map(lambda var:var*2, seq)))

[2, 4, 6, 8, 10]

👉Jupiter notebook link :)

👉git

Credits & References

Lambda Functions with Practical Examples in Python — How, when to use, and when not to use Lambda functions by towardsdatascience.com

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Edited at Dec_2021 — completing the code to run in pycharm:)