Python Concatenate String and Int

Introduction

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.

Example

Let’s look at an example for concatenating a string (str) and an integer (int) using the + operator.

current_year_message = 'Year is '

current_year = 2018

print(current_year_message + current_year)

The desired output is the string: Year is 2018. However, when we run this code we get the following runtime error:

Traceback (most recent call last):
  File "/Users/sammy/Documents/github/journaldev/Python-3/basic_examples/strings/string_concat_int.py", line 5, in <module>
    print(current_year_message + current_year)
TypeError: can only concatenate str (not "int") to str

So how do you concatenate str and int in Python? There are various other ways to perform this operation.

Using the str() Function

We can pass an int to the str() function it will be converted to a str:

print(current_year_message + str(current_year))

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:

print("%s%s" % (current_year_message, current_year))

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.

print("{}{}".format(current_year_message, current_year))

The current_year integer is type coerced to a string: Year is 2018.

Using f-strings

If you are using Python 3.6 or higher versions, you can use f-strings, too.

print(f'{current_year_message}{current_year}')

The current_year integer is interpolated to a string: Year is 2018.

Conclusion

You can check out the complete Python script and more Python examples from our GitHub repository.