Altcademy - a Forbes magazine logo Best Coding Bootcamp 2023

What is concatenate in Python

Understanding Concatenation in Python

When you're starting your journey in the world of programming, you'll come across a variety of concepts that form the building blocks of writing code. One such fundamental concept is "concatenation". In the simplest terms, concatenation is a fancy word for combining things together, end-to-end. It's like stringing pearls onto a necklace or adding cars to a train. In Python, you can concatenate text strings, lists, and other sequences.

Concatenating Strings

Strings are sequences of characters, and in Python, you can concatenate them using the plus (+) operator. Imagine you have two pieces of text: "Hello" and "World". Concatenating them would give you "HelloWorld". It's as simple as adding numbers, but instead of a sum, you get a longer string.

first_word = "Hello"
second_word = "World"
combined_words = first_word + second_word
print(combined_words)  # Output: HelloWorld

Notice that there is no space between "Hello" and "World" in the output. If you want a space, you need to include it explicitly:

combined_words_with_space = first_word + " " + second_word
print(combined_words_with_space)  # Output: Hello World

Concatenating Lists

Lists in Python are like baskets that can hold different items. Concatenating lists means you're putting the contents of one basket into another to make a bigger basket of items.

first_list = [1, 2, 3]
second_list = [4, 5, 6]
combined_list = first_list + second_list
print(combined_list)  # Output: [1, 2, 3, 4, 5, 6]

Concatenation and Immutability

An important term to understand when working with concatenation is "immutability". In Python, some objects, like strings, are immutable, which means they cannot be changed after they are created. When you concatenate strings, you are not actually modifying the original strings but creating a new string that is the combination of the original strings.

greeting = "Hello"
name = "Alice"
personal_greeting = greeting + " " + name
print(personal_greeting)  # Output: Hello Alice
print(greeting)  # Output: Hello
print(name)  # Output: Alice

In this example, neither greeting nor name is changed; personal_greeting is a completely new string.

Concatenation with Other Operators

While the plus (+) operator is the most common way to concatenate in Python, there's another operator that can be used specifically with strings: the multiplication (*) operator. This might sound strange, but it's like saying "give me this string this many times".

laugh = "ha"
lots_of_laughter = laugh * 3
print(lots_of_laughter)  # Output: hahaha

Concatenation Errors to Avoid

When you're concatenating, it's important to remember that you can only concatenate like with like. This means you can concatenate strings with strings and lists with lists, but not strings with lists or numbers with strings without converting them to the same type.

# This will not work and will raise a TypeError
number = 123
text = "abc"
print(number + text)

To make the above code work, you need to convert the number to a string using the str() function:

number = 123
text = "abc"
print(str(number) + text)  # Output: 123abc

Concatenation in Real-World Programming

Concatenation is not just an academic concept; it's used all the time in real-world programming. For instance, when you're working on a website and you need to put together a full URL from different parts, or when you're writing a program that generates a personalized message to a user, you'll be using concatenation.


In the tapestry of programming, concatenation is the thread that allows you to weave together separate strings of characters or items in lists to create something new and meaningful. It's a simple yet powerful tool in your coding arsenal. As you continue your programming journey, you'll find that understanding and using concatenation effectively will open up a world of possibilities. Whether it's crafting a message, building a URL, or simply bringing together data, mastering concatenation is a step towards becoming a proficient Python programmer. Keep experimenting, keep learning, and most importantly, have fun with it! After all, the art of coding is a bit like magic—combining simple elements to create something extraordinary.