Python: Concatenate a String and Int (Integer)
In this tutorial, you’ll learn how to use Python to concatenate a string and an int (integer). Normally, string concatenation is done in Python using the + operator. However, when working with integers, the + represents addition. Because of this, Python will raise an error, a TypeError to be exact, when the program is run.
By the end of reading this tutorial, you’ll have learned how to use Python to concatenate a string and an int using a number of methods. You’ll have learned how to use the str() function, the .format() method, % format specifier, and – my personal favourite – Python f-strings.
The Quick Answer: Use f-strings or str() to Concatenate Strings and Ints in Python
Table of Contents
Concatenate a String and an Int in Python with +
In many programming languages, concatenating a string and an integer using the + operator will work seamlessly. The language will handle the conversion of the integer into a string and the program will run fine. In Python, however, this is not the case. Due to the dynamic typing nature of Python, the language cannot determine if we want to convert the string to an integer and add the values, or concatenate a string and an int. Because of this, the program will encounter a TypeError .
Let’s see what this looks like when we simply try to concatenate a string and an integer in Python using the + operator:
The TypeError that’s raised specifically tells us that a string and an integer cannot be concatenated. Because of this, we first need to convert our integer into a string. We can do this using the string() function, which will take an input and convert it into a string, if possible.
Let’s try running our running program again, but this time converting the int into a string first:
We can see that by first converting the integer into a string using the string() function, that we were able to successfully concatenate the string and integer.
In the next section, you’ll learn how to use Python f-strings to combine a string and an integer.
Concatenate a String and an Int in Python with f-strings
Python f-strings were introduced in version 3.6 of Python and introduced a much more modern way to interpolate strings and expressions in strings. F-strings in Python are created by prepending the letter f or F in front of the opening quotes of a string. Doing so allows you to include expressions or variables inside of curly braces that are evaluated and converted to strings at runtime.
Because of the nature of f-strings evaluating expressions into strings, we can use them to easily concatenate strings and integers. Let’s take a look at what this looks like:
One of the great things about f-strings in Python is how much more readable they are. They provide us with a way to make it immediately clear which variables are being joined and how they’re being joined. We don’t need to wonder about why we’re converting an integer into a string, but just know that it’ll happen.
In the next section, you’ll learn how to use the .format() method to combine a string and an integer in Python.
Concatenate a String and an Int in Python with format
The Python .format() method works similar to f-strings in that it uses curly braces to insert variables into strings. It’s available in versions as far back as Python 2.7, so if you’re working with older version this is an approach you can use.
Similar to Python f-strings, we don’t need to worry about first converting our integer into a string to concatenate it. We can simply pass in the value or the variable that’s holding the integer.
Let’s see what this looks like:
We can see here that this approach returns the desired result. While this approach works just as well as the others, the string .format() method can be a little difficult to read. This is because the values placed into the placeholders are not immediately visible.
In the next section, you’ll learn how to concatenate a string an int in Python using the % operator.
Concatenate a String and an Int in Python with %
In this final section, you’ll learn how to use % operator to concatenate a string and an int in Python. The % operator represents an older style of string interpolation in Python. We place a %s into our strings as placeholders for different values, similar to including the curly braces in the example above.
Let’s see how we can combine a string and an integer in Python:
We can see that this returns the same, expected result. This approach, however, is the least readable of the four approaches covered here. It’s included here more for completeness, rather than as a suggested approach.
In this tutorial, you learned how to use Python to concatenate a string and an int. You learned why this is not as intuitive as in other languages, as well as four different ways to accomplish this. You learned how to use the + operator with the string() function, how to use Python f-strings, and how to use the .format() method and the % operator for string interpolation.
To learn more about the Python string() function, check out the official documentation here.
Python – Concatenate string and int
In Python, we normally perform string concatenation using the + operator. The + operator, however as we know, is also used to add integers or floating-point numbers.
So what would happen if we have a string and an int on both sides of the operand?
Since Python is a dynamically typed language, we would not face any error during compilation, but rather, we get a Runtime Error. (More specifically, a TypeError exception is raised)
The below snippet proves this:
So, since we cannot directly concatenate an integer with a string, we need to manipulate the operands so that they can be concatenated. There are multiple ways of doing this.
1. Using str()
We can convert the integer to a string, via the str() function. Now, the new string can now be concatenated with the other string to give the Output;
This is the most common way to convert an integer to a string.
But, we can use other methods as well.
2. Using format()
The output remains the same as before.
3. Using ‘%’ format specifier
While we can specify that both a and b are strings, we can also use C-style format specifiers ( %d , %s ) to concatenate an integer with a string.
The output remains the same for the above code.
4. Using f-strings
We can use Python f-strings on Python 3.6 or above to concatenate an integer with a string.
5. Printing the string using print()
If we want to directly print the concatenated string, we can use print() to do the concatenation for us.
We join a and b using a null string separator ( sep ), since the default separator for print() is a space (” “).
In this article, we learned how to concatenate an integer to a string using various methods.
How To Concatenate String and Int in Python
Python supports string concatenation using the + operator. In most other programming languages, if we concatenate a string with an integer (or any other primitive data types), the language takes care of converting them to a string and then concatenates it.
However, in Python, if you try to concatenate a string with an integer using the + operator, you will get a runtime error.
Let’s look at an example for concatenating a string ( str ) and an integer ( int ) using the + operator.
The desired output is the string: Year is 2018 . However, when we run this code we get the following runtime error:
So how do you concatenate str and int in Python? There are various other ways to perform this operation.
In order to complete this tutorial, you will need:
- Familiarity with installing Python 3. And familiarity with coding in Python. How to Code in Python 3 series or using VS Code for Python.
This tutorial was tested with Python 3.9.6.
Using the str() Function
We can pass an int to the str() function it will be converted to a str :
The current_year integer is returned as a string: Year is 2018 .
Using the % Interpolation Operator
We can pass values to a conversion specification with printf-style String Formatting:
The current_year integer is interpolated to a string: Year is 2018 .
Using the str.format() function
We can also use the str.format() function for concatenation of string and integer.
The current_year integer is type coerced to a string: Year is 2018 .
If you are using Python 3.6 or higher versions, you can use f-strings, too.
The current_year integer is interpolated to a string: Year is 2018 .
You can check out the complete Python script and more Python examples from our GitHub repository.
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Python число в строку
Чтобы конвертировать число в строку, используйте встроенную функцию str() . Эта функция в качестве входящих данных принимает число (или другой тип данных), а в результате выдает строку.
Вот один пример:
Если число является значением переменной, конвертировать его можно следующим образом:
Конкатенация строк и чисел в Python
Иногда возникает необходимость сконструировать строку, содержащую число из другой переменной. Вот пример, как это делается:
Избегаем преобразования типов данных
Когда разработчикам нужно объединить число и строку, они обычно применяют функцию str() непосредственно перед выводом данных на экран. Например: