Lambda function in python

 what is a Lambda Function?

In contrast to normal functions, a lambda function is an anonymous function that evaluates and returns a single expression and can take any number of arguments. It is defined without a name.

The syntax of a lambda function in Python is as follows:

parameters of lambda: expression

A lambda function's anatomy consists of three parts:

The body is the expression for the parameters that are being evaluated by the lambda function.

Note that, in contrast to a normal function, we do not surround the parameters of a lambda function with parentheses. The keyword lambda is an analog of def in normal functions.

The parameters support passing positional and keyword arguments, just like normal functions. We use a comma to separate the parameters of a lambda function that takes two or more.

A lambda function is only used once to evaluate a single short expression—ideally, one line—and we won't use this function again.

How a Python Lambda Function Works

The preceding lambda function takes one argument, increases it by one, and returns the result. When we call our lambda function, parentheses are added to the lambda function's entire construction and the argument we passed to it.

The parameter of our lambda function does not have parentheses surrounding it.

With a lambda function, we can execute the function immediately after it is created and receive the result, as can be seen in the code above. The immediate invoked function execution, or IIFE, is the term for this.

A lambda function with multiple parameters can be made. In this instance, we use a comma to separate the parameters in the definition of the function.

The arguments to such a lambda function are listed in the same order and separated by commas when executed.

Scalar values

When you run a lambda function on a single value, this happens. The function was created and immediately executed in the preceding code. This is an illustration of a function expression that is immediately invoked.

Lists

Filter().This is a built-in Python library that only returns values that meet a certain set of criteria. The syntax (function, iterable) is filtered. Any sequence, including a list, set, or series object, can be iterable.

Map().Another Python library that comes built-in features the syntax map(function, iterable).

Based on a function, this returns a modified list in which each value in the original list has been altered.

Series object

A column in a data frame is a Series object, or, to put it another way, a sequence of values and their corresponding indices. Values within a Pandas data frame can be manipulated with the help of lambda functions.

Lambda with the Pandas Apply() function. Every column element is subjected to the operation performed by this function. 

Lambda on Dataframe object

Unless I want to change the entire data frame with a single expression, I typically use Lambda functions only on specific columns (series objects).

Conclusion

If your function only contains one small expression, lambda functions are an efficient way to write functions. They are typically not used by novice programmers, but you have seen how to use them at any level here.

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