How to concatenate Strings on Python
Short answer: the simplest way to concatenate strings in Python is the + operator ("Hello " + name). When you mix text and variables, f-strings are the most readable option (f"Hello {name}"), and to join many strings from a list you can use " ".join(words). Numbers must be converted with str() before using + (Python documentation on f-strings).
String concatenation is the process of adding two strings together in one. The easiest way to concatenate strings in Python would be to use the format string method. This method consists on adding the letter "f" before the string quote marks like this f"Hello world" , then you can concatenate variables by calling them between brackets {} inside the string quote marks. Here is an example of how to use it:
name = "4Geeks"
print(f"Hello from {name}!")
#Output -> Hello from 4Geeks!In the previous example, we are using the variable name to concatenate it to the string.
String concatenation is a common action we, as software developers, have to deal with in almost any project. There are many ways you can concatenate strings, you can use any of them so pick the one that suits you the most.
Concatenate strings on Python using the + operator
The most familiar way to concatenate strings for most people is the + operator. Check this example that explains how it works:
name = "Alex"
print("Hello my name is " + name + " and I'm a developer")
#Output-> Hello my name is Alex and I'm a developerNotice the space after
isand beforeand, if we didn't add them, then the output would have looked like this:Hello my name isAlexand I'm a developer. Remember to add the spaces when needed.
Concatenate strings using the += operator
We can use the += operator to concatenate strings as well, it's pretty similar to using the + operator, but in this case the result is assigned back to the same variable (strings are immutable, so Python creates a new string instead of modifying the original one).
#Concatenate using the += operator
fullname = "Alex "
lastname = "Smith"
fullname += lastname
print(fullname)
#Output-> Alex SmithNotice that there is a space inside the string, otherwise fullname's value would be "AlexSmith". Remember to add the spaces when needed.
Concatenate an int or float value with text using str()
Numbers and strings are data type completely different. When we want to add a number (int, float, etc) to a string, we will need to use the str() to convert that number into a string.
# Concatenate using the + Operator with numbers
geeks_word = "Geeks"
geeks_number = 4
print("At " + str(geeks_number) + geeks_word + " Academy we love Python! <3")
#Output-> At 4Geeks Academy we love Python! <3As stated above, we are adding spaces for the render to respect writing rules.
If we would not convert the geeks_number number variable to a string, we would receive the following error letting you know you are trying to concatenate an Integer with a String.
TypeError: can only concatenate str (not "int") to strConcatenate strings on Python using the f-Strings
Python f-Strings (formatted string literals) makes writing strings faster and much easier. This option was introduced on Python 3.6 so keep in mind backward compatibility when using it.
This is one of the most used methods among experienced developers because of the ease to insert variables into the curly brackets. The variable(s) will be evaluated and a string representation will be displayed.
Implementation:
#Concatenate using the f-Strings method
geek_word = "Geeks"
print(f"Showing the geek_word variable: {geek_word} using f-String")
#Output-> Showing the geek_word variable: Geeks using f-StringMaking use of the f-Strings concatenation, we don't need to convert numbers (Int, Float, etc) to string to be able to display them inside the curly brackets.
#Concatenate using the f-Strings method with numbers
geek_word = "Geeks"
geek_number = 4
print(f"At {geek_number}{geek_word} Academy we love Python! <3")
#Output-> At 4Geeks Academy we love Python! <3Concatenate using .format()
Another way to concatenate strings in Python is by making use of the format() method. It works similar to f-Strings since they both use curly brackets {} to insert variables but is available from version 2.6.
This method doesn't need either to convert the number values into strings.
#Concatenate using the .format() method
geek_word = "Geeks"
geek_number = 4
text = "{}{} Academy".format(geek_number, geek_word)
print(text)
#Output-> 4Geeks AcademyAs you can see, the result returned is the expected one, with no space between the number and the word because there is none between the two {} placeholders.
Concatenate using % operator
The % operator is an older way to concatenate strings that work very similar to the .format() method. We use %s as placeholders for different values, as we did with the curly brackets in previous examples.
#Concatenate using the % Operator
geek_word = "Geeks"
geek_number = 4
text = "%s%s Academy" % (geek_number, geek_word)
print(text)
#Output-> 4Geeks AcademyConcatenate using the * Operator
The use of the * Operator is not a concatenation in the way we have been doing so far. The * Operator is used for multiplication and that's exactly what it does, multiplying for the amount given the string.
#Concatenate using the * Operator
str1 = "4Geeks Academy "
print(str1*3)
#Output-> 4Geeks Academy 4Geeks Academy 4Geeks Academy If you format the string variable correctly (leaving a space at the end of the sentence/word), this is the best way to repeat a line of text as many times as you may need.
Recommended Material
If you want to learn more about how to concatenate strings in Python and explore the different methods available, we invite you to check out this interactive tutorial.
👉 Explore this tutorial on string concatenation in Python!
In this tutorial, you will learn:
- How to use modern and traditional methods to concatenate strings.
- The importance of handling different data types, such as numbers and strings.
- We will practice creating variables, loops, and some functions. Additionally, we will cover best practices for writing more readable and efficient code.
Don’t miss it! This is an essential resource to become a more effective Python developer.
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Frequently asked questions
How do I concatenate a list of strings in Python?
Call join() on the separator you want, for example " ".join(words) for spaces or ", ".join(words) for commas. It joins every element in one step and is faster than adding strings in a loop. All items must already be strings, so convert numbers first with " ".join(map(str, numbers)) to avoid a TypeError.
What is the most efficient way to build a string inside a loop?
Append each piece to a list and call "".join(parts) once after the loop. Strings in Python are immutable, so every + or += creates a new string and copies the previous content, which becomes slow when repeated many times. For a few concatenations the difference is negligible, so choose whichever form is most readable.
How do I add a line break when concatenating strings?
Insert the newline character \n where the break should appear, for example "First line" + "\n" + "Second line" or f"{first}\n{second}". To place many strings on separate lines, use "\n".join(lines). When printing, print(a, b, sep="\n") produces the same output without building the combined string yourself.
Can Python join strings without using any operator?
Yes, but only with literals. Python automatically joins string literals written next to each other, so "Hello " "world" becomes "Hello world" at compile time. This is handy for splitting a long string across several lines inside parentheses. It does not work with variables, which still need +, an f-string, format() or join().