Python Programming 101 - Lambda | Map | Filter | Reduce | *args and **kwargs

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In this tutorial, we will learn about one of the interesting topics that play a vital role in python programming .i.e. lambda function. Lambda functions change the definition of traditional functions that we are using in our day to day life.

However, with the help of the lambda function, we are able to cover the three subtopics such as map, filter, and reduce.

Lambda Function

Lambda function can be called as anonymous/one-liner function.

How lambda function can be useful?

1. Lambda can be useful when we want to write a function in a  compact way or in a one-liner.
2. Lambda function can be useful when we want the function to be part of another function. Or we can say that when we want one function to pass arguments to another function where we can use lambda function.

Let's understand the paradigm of a lambda function using an example.

Explanation:

This code explains the compact nature of the lambda function. You can see that in the code first in the case of traditional or regular python function what are the required steps are necessary for writing code 1. Need to define the function using def keyword (def function_name(parameter)) 2. Under the function, the definition needs to write the statement or body of the function. 3. Last step function calling and parameter passing. The whole python regular function is the three-step process and we can reduce at times when we need some compact structured way using lambda function.

In Lambda function, we are declaring only variable and after that using the lambda keyword we are writing the actual working of code and at last, we are passing the parameter. That's how simple the lambda function is.

Let's see another example of the lambda function.

Explanation:

In this example, we are using another concept of lambda function in which we are passing the lambda function parameter to another function. We are using two variables and taking input from the user of multiplicand and multiplier using type casting for converting a string to an int type. And after that passing multiplier value to lambda function and multiplicand value to the regular function and use those two values for general multiplication. With the help of this example, we all are aware that we can lambda python function in parameter passing also.

Map

A map is used to apply a function in every element in a list.

Properties:
1. Works with regular or lambda function
2. Takes list as an argument
3. Provide a modified list

Filter

A filter is used for filtering the list for which the functions returns true.

Properties:
1. Works with regular or lambda function
2. Takes list as an argument
3. Filter the list by applying a certain condition is true.

Reduce

A Reduce is used for reducing the list by performing repetition operations over the pairs of lists. Reduce comes under the functools module.

Properties:

1. Works with regular or lambda function
2. Takes list as an argument
3. Reduce the list 
4. Using functools module

Example of Map, Filter and Reduce:

*args vs **kwargs

Important Point (Both are used when we are dealing with unpredictable datasets or value)

*args - It is used to pass a big list of argument or unpredictable list of argument

**kwargs - keyword argument

Working of both *args and **kwargs are same only major difference between both of them is when are dealing with a list of elements we need to use *args and when we are dealing with keyword argument such as dictionaries like data-type we need to use **kwargs.


Let's discuss with the help of an example.



In this example, we are declaring two functions with different parameters set one for a list of arguments and one for keyword argument. The syntax is self-explanatory all we are using simple python function syntax for parameter passing and function calls except when we are passing a simple list of arguments we are using *args and when we are passing keyword argument dictionary like we are using **kwargs.

Different Scenario of using *args and **kwargs:

1. Both can be used in the same function with a different function call

2. Both can be used in the same function with the same function call

3. Order Strictly followed

Note:
We have to follow the concept of ordering while using *args and **kwargs both strictly follow the nature of the order.

First (Normal Parameter) > Second (*args) > Third (**kwargs)


In the next tutorial, we will study decorators, enumerate functions, join, and Indexing/Slicing.

Click here for the next tutorial.

For Complete Python Programming 101 tutorial series ( Click here ). 

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