enumerate() is the solution!!

The enumerate() function adds a counter to an iterable and returns it in a form of an enumerated object. This object can be used directly in for loops and even can be converted into a list of tuples.

Here is its syntax:
enumerate(iterable, start=0)

An iterable must be a sequence or some object which supports iteration. As Python is a 0-indexed language, the iteration counter starts at 0 by default. Certainly, you can change the starting number of the iteration counter.

Let’s continue with the colors example from the previous function.

colors = ['red', 'yellow', 'green', 'black']
result = enumerate(colors)

In this example, the result is an enumerated object, which can be directly used in a for loop and even can be converted into a list.

Zip Function

The zip() function is used to use the similar index of multiple containers so that they can be used as a single entity.

The syntax is as simple as the definition:
zip(iterables)

It produces a tuple with one item from each container or iterable.

Let’s have an example of two lists.

colors = ['red', 'yellow', 'green', 'black']
fruits = ['apple', 'pineapple', 'grapes', 'cherry']

Using zip() function in a for loop,

zip() is often used in cases where the containers are assumed to be of equal length. However, if the containers have different lengths, the function zip() stops when the smallest container is exhausted. An example is below.

Using zip() function when containers have different sizes or lengths,

You can pass lists, tuples, sets, or dictionaries through the zip() function.

Filter Function

Often, we need to process an iterable and extract those items that satisfy a given condition.

filter() can save your time and efforts!!

The filter() extracts elements from an iterable such as a list, tuples where the extracted elements are the ones where the function returns true.

Here is a syntax:
filter(function, iterable)

For easier digestion, let’s take an example. Let’s create a function to check if the word is in upper case or not. And then use the filter() to extract all the words from the iterable which are in uppercase.

Here is official documentation about filter().

? Learn how to define a function in a single line using Ternary conditional.

Lambda Function

Lambda functions are used to create anonymous functions i.e. functions without a name. They are useful when we need to create a function to do a single operation and can be written in one line. Its syntax is:

lambda parameters: expression

? Lambda functions can have any number of parameters but can only have one expression.

For example, lambda x: x+2

That’s it!! Just now I created a function that takes a single input parameter x and adds 2 to it.

However, as you can see this is an anonymous function, it can not be called at a later stage. Hence, to call it any time in the program, the lambda function can be assigned to a function object like this,

add2 = lambda x: x+2

Calling this function is exactly the same as calling a function that was defined with the def keyword. For example,

add2(10) # It will return 12 as output

The lambda function can be a good one-liner in some situations such as List comprehensions.

As shown in the above picture, newlist is generated with a single line of code by using the lambda function.

Summing up,

I found these built-in functions quite handy while using Python for Data Analysis as well as complex automation tasks. Some of them such as zip() , map() are useful in many cases while others such as Lambda function serve as the best one-liner in some situations.

Source: https://towardsdatascience.com/5-most-reliable-functions-you-should-know-in-python-programming-654db1bb89f