Python supports object-oriented programming and provides a concise, readable, easy-to-learn syntax. These qualities make Python one of the most popular programming languages. In this article, we learn about some of the most used functions in Python to get you started. 

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In this article, we’ll cover:

• Top 16 Python Functions You Must Know
• FAQs on the Top 16 Most Used Functions in Python

Top 16 Python Functions You Must Know

While there’s no dearth of useful built-in Python functions, this article focuses on 16 powerful Python functions you should definitely know. Let’s jump right in!

1. The append() Function in Python 

Python’s append() function takes a single item as an input parameter and adds it to the end of the given list. In Python, append() doesn’t return a new list of items; it returns no value. It just modifies the original list by adding the item to the end of the list. 

After executing append() on a list, the size of the original list increases by one. The item in the list can be a string, number, dictionary, or even another list (because a list is an object too). When a list is appended to the original list, it is added as a single object. The addition of the appended list happens, as usual, at the end of the original list.

2. The eval() Function in Python 

Python’s eval() function is a built-in function that evaluates a specified expression and executes it if it’s a legal Python statement. In simpler words, eval() evaluates the given string like a Python expression and returns a number as the result of that evaluation. 

In Python, eval() works by parsing the expression argument and evaluating it as a Python expression. eval() is usually used in Python when there’s a need to either evaluate mathematical expressions or evaluate the string into code. 

3. The getattr() Function in Python 

Python getattr() function is a built-in function used to access the attribute value of an object. We also use it to execute the default value if the attribute/key does not exist. The conventional method of accessing the attribute value generally takes less time than getattr(). But if we need to use default values in case of missing attributes, getattr() is appropriate.

We use the Python function getattr() in web developments involving optional form attributes. We also use it in Machine Learning feature collection cases, where features go missing at times in data collection.

4. The join() Function in Python 

The join() function in Python is a built-in string method. It joins all elements in an iterable with a given string separator into one string. It returns a string with all the elements joined with the desired separator. Please note that the desired separator can only be of the type string. Also, the elements inside the iterable need to be strings.

5. The lower() Function in Python 

Python’s lower() function converts all the uppercase characters in a string to lowercase characters and returns the modified string. 

One common application of the lower() function in Python is to check if the given two strings are the same or not. We’ll show you how to do this using an example later in the post.

Note: If you want to convert all characters in a string to uppercase, use the Python function upper(). And if you’re going to swap between lowercase and uppercase, use the swapcase() function in Python. 

6. The upper() Function in Python 

Python’s upper() function converts all the lowercase characters in a string to uppercase characters and returns the modified string. One common application of the upper() function in Python is to check if the given two strings are the same or not. We’ll show you how to do this using an example later in the post.

Note: If you want to convert all characters in a string to lowercase, use the Python function lower(). And if you’re going to swap between lowercase and uppercase, use the swapcase() function in Python. 

7. The max() Function in Python 

The max() function returns the maximum value in an iterable or out of two or more given values in Python. It can be used in two forms: with objects or with iterables. Unlike max() in C/C++, in Python, max() can take in any type of object and return the largest object. 

The function that will form the basis for our maximum value calculation can also be specified. For example, we can evaluate the max value of strings based on lexicography, string length, etc. 

For strings, it by default returns the lexicographically largest value. However, we can specify the basis of max calculation to be another function like “len” for string length. Finally, when we pass an iterable to max() in Python, it returns the largest item in the iterable.

8. The min() Function in Python 

The min() function returns the minimum value in an iterable or out of two or more given values in Python. It can be used in two forms: with objects or with iterables. Unlike min() in C/C++, in Python, min() can take in any type of a set of objects and return the largest object. 

The function that will form the basis for our minimum value calculation can also be specified. For example, we can evaluate the min value of strings based on lexicography, string length, etc. For strings, it by default returns the lexicographically smallest character. 

However, we can specify the basis of min calculation to be another function like “len” for string length. Finally, when we pass an iterable to min() in Python, it returns the smallest item in the iterable.

9. The range() Function in Python 

Python range() function is a built-in function we can use to generate a sequence of numbers within a given range. Through the number of arguments passed to the function, we can control where that sequence of numbers will begin and end, along with the difference between two consecutive numbers in the series. 

Python range() function is often used to iterate through a sequence using a for or while loop.

10. The reduce() Function in Python

Python’s reduce() function implements a mathematical technique called folding or reduction. This technique involves reducing a list of items to a single cumulative value. Python’s reduce() operates on any iterable. Also, for using reduce() in Python 3.x, reduce() needs first to be imported using an import statement to the current scope.  

reduce() takes an existing function and applies it cumulatively to every item in the given iterable. It returns a single return value. Here’s how it works: 

• The function is called on the first two items in the iterable, which gives a partial result
• That partial result is used with the third item in the iterable to give another partial result
• This process continues until the iterable is exhausted and a single cumulative value is returned

11. The replace() Function in Python 

The built-in function replace() in Python replaces all or some specified number of occurrences of a substring in the original string with a different substring. It returns a copy of the original string with instances of the old substring replaced with the new desired substring.

12. The round() Function in Python 

The round() function in Python rounds a number to a specific decimal place and returns a floating-point number rounded as per our specifications. It takes the following arguments:

1. Any number 
2. The number of decimal places (optional)

The number of decimal places is set to zero by default. So the round() function returns the nearest integer to the number passed if the number is the only argument passed.

13. The slice() Function in Python 

Python’s slice() function returns a slice object that specifies how to slice a sequence. We can set where to start and end the slicing as well as the slicing step size. The sequence of objects to be sliced can be of any type, such as tuple, string, bytes, list, range, the object that implements __getitem__() and __len__(), etc.

14. The sorted() Function in Python 

Python sorted() function returns a sorted list with elements taken from an iterable object. The sorted() function sorts any sequence. This sequence can be, say, like a tuple or a list. sorted() always returns a list with the elements in sorted order. If you’re wondering how to sort a list in Python without the sort() function, you can use sorted(). Note that sorted() does not modify the original sequence. 

15. The split() Function in Python 

The split() function in Python operates on strings. It takes a string as input and splits it wherever it encounters a “separator” (a character that acts as a marker for the split). The output is a list of strings, where the elements are the individual parts of the input string after the splits. 

By default, split() assumes the separator to be whitespace (“ ”). So if we call the split() function for a typical English sentence, the output would be a list of words in that sentence. Suppose the input is a string of words separated by commas (“,”), and we specify that the separator should be the comma character. In that case, the output will be a list where the elements are the individual words of the input string.

16. The strip() Function in Python 

Python’s strip() function is a built-in function that removes specific leading and trailing characters from the start and end of the original string. These characters to remove are given as an argument to strip() for removal. 

If we provide no string as an argument, the strip() function removes the leading and trailing whitespaces as a default. If no leading or trailing strings match the argument, the new string returned is the same as the original string.

FAQs on the Top 16 Most Used Functions in Python

Q1. What are the most useful functions in Python?

Some of the most useful functions in Python are print(), abs(), round(), min(), max(), sorted(), sum(), and len().

Q2. Why are functions used in Python?

Functions are just bundled sets of instructions that we can repeatedly use without having to write them again. They make the code more concise and readable in any language, including Python.

Q3. What are the four types of functions in Python?

Built-in, recursion, lambda, and user-defined functions are Python’s four types of functions.

Q4. What are upper() and lower() functions in Python?

Both upper() and lower() functions are built-in functions for string handling in Python. For a given string, upper() converts the string to all uppercase, while lower() converts the string to all lowercase. 

Q5. How many built-in Python functions are there?

Python 3.6 has 67 built-in functions!

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