How can I concatenate str and int objects in Python?

In many coding languages, when you try to combine a string with a number, the number is usually converted into a string automatically so both parts can be joined together. This is called implicit type conversion.

With the + operator for concatenating a string with a numerical value, Python does not perform the implicit type conversion. Instead, it throws an error (specifically a TypeError) because it expects both operands to be strings. The following are the various methods to do it:

• Using the str() Function
• Using f-strings
• Using join() method with a list comprehension
• Using string formatting with named placeholders

Using the str() Function

The str() function converts an integer to a string. This allows you to concatenate it with another string using the + operator.

Example

In the following example, we converted the integer (42) into a string using the str() function and concatenated the two strings using the + operator ?

my_string = "The answer is: "
my_number = 42
result = my_string + str(my_number)
print(result)

The output of the above code is ?

The answer is: 42

Using f-strings

F-strings, or formatted string literals, allow us to embed expressions inside string literals by prefixing them with f. We can directly insert variables and expressions within curly braces {} inside the f-string.

Example

This example demonstrates joining a string and an integer using an f-string. The number inside the curly braces {} is automatically converted into a string and combined with the string ?

my_string = "Hello"
my_number = 123
result = f"{my_string}{my_number}"
print(result)

The output of the above code is ?

Hello123

Using join() Method with a List Comprehension

Python's join() method is useful when combining multiple values, especially in a list. When used with a list comprehension, each item (like numbers) can be turned into strings and joined with a separator like a comma.

Example

This example shows how to combine a list of numbers with text. Each number is first turned into a string and then joined together with commas using .join() ?

my_string = "The numbers are: "
my_numbers = [1, 2, 3, 4]
result = my_string + ", ".join(str(num) for num in my_numbers)
print(result)

The output of the above code is ?

The numbers are: 1, 2, 3, 4

Using String Formatting with Named Placeholders

This method improves readability by assigning names to placeholders in a string. The .format() function then replaces these with actual values.

For instance, if we write placeholders like {name} in the string and use format(name="value") to fill them. This makes the code more readable and easier to understand, especially when working with multiple values.

Example

This example demonstrates how to use named placeholders in a string. The placeholders are replaced with actual values using the .format() method ?

my_string = "I have {num_apples} apples and {num_oranges} oranges."
num_apples = 5
num_oranges = 3
result = my_string.format(num_apples=num_apples, num_oranges=num_oranges)
print(result)

The output of the above code is ?

I have 5 apples and 3 oranges.

Comparison

Conclusion

Use f-strings for modern Python code as they are the most readable and efficient. Use str() for simple concatenation and .format() for complex formatting needs.