#python lambda

[codeonedigest]

What is Python Lambda Function? | Learn Python Anonymous Functions in 1 minute by CodeOneDigest is a YOUTUBE channel. We publish technology

Python Lambda Functions are anonymous function means that the function is without a name. As we already know that the def keyword is use

[aisangam]

Python Lambda, Map, Filter and Reduce Operations with Python List

Python Lambda, Reduce, Filter and Map has very important significance especially while working with Python List. To explain every function both with live code an detailed description, Please see this video and click on the links provided in the description for viewing both the code and description of each function. Hope this would be useful to you especially for those who are appearing for python related programming interviews. Please click on the link to see the video

https://www.youtube.com/watch?v=R66CRZk8Vqw&feature=youtu.be

[aisangam]

Python Reduce Function Use Case

Python reduce is also very effective function while you need to apply some function to every element of the list or you want to do some comparison among different elements of the list . Please see the following code and description for finding the maximum element from the python list using reduce and lambda function.

https://github.com/AISangam/Python-Reduce

[sikrob]

Python: Sorting Lists of Objects with Lambda

While playing around with Python, my brother directed me to a nifty piece of Python that continues to expand Python's dominance in my usage, and that is Python's sorting stuff for its lists. Specifically, some more interesting usage of sort() I wasn't aware of previously.

In Python, you can store pretty much anything in a list, but at first glance you can't use all the great stuff with that lists come with – most specifically the built-in sorting function, in my case. This lead me to cobble together a quicksort implementation which gave me some fun but tedious debugging. However, it turns out there is a way to avoid dealing with that altogether thanks to some extended functionality of the sort() method that I didn't know about.

Sort() can accept a key that allows you to do something with the elements of the list before sorting them. For example, you can sort a list by length by using "mylist.sort(key=len)", which will call the len() on each element of the list and then sort the elements by the length found by len(). Key accepts any function that takes an argument, which brings us to lambda.

Lambda is cool because it lets you define a function inline and use it, which is nice in exactly the scenario of sorting a list of objects. I'm not going to dive into lambda in-depth here as I've only just learned of it, but let's look at what it can do for my specific use case. Lambda works like so "lamda x:x+1", which in this case takes an argument and adds one to it; a context in which this would make sense, for example, would be "mylist.sort(key=lambda x:x%8)" where the result would be the values of a list sorted by their modulus 8 value. For example:

>>> myList = list(range(1,30,3)) >>> myList [1, 4, 7, 10, 13, 16, 19, 22, 25, 28] >>> myList.sort(key=lambda x:x%8) >>> myList [16, 1, 25, 10, 19, 4, 28, 13, 22, 7]

As you can see, rather than sorting in the default ascending order, we have 16, which is 0 when %8, followed by 1 and 25, which are both 1 when %8, and so on.

At this point it is now a simple matter of defining the call you want to make to lambda so that you can get the result you want. Suppose you have a class "person" with a member "age" and you want to display your people by their age but the people are added in an arbitrary order. All you need to do is, before printing the elements of the list, sort the list by age using a lambda function as the key. In this case, that might look like this:

myPeople.sort(key=lambda Person:Person.age)

This take a Person object and calls the age member of that object to use as the sorting key.

And voila! You can now sort lists of objects using information in the objects for the built-in list.sort() method! This is a boon in terms of speed. I don't know off hand what sorting algorithm sort() uses, of course, and lambda may have some overhead as well, so I can't speak to whether this is a really optimal solution, but certain for easing the pace of development ahead, this is a nice solution that promises to have good implication for other applications.