Python String join()

Summary: in this tutorial, you’ll learn how to use the Python String join() method to concatenate strings in an iterable into one string.

Introduction to the Python String join() method #

The string join() method returns a string which is the concatenation of strings in an iterable such as a tuple, a list, a dictionary, and a set.

The following shows the syntax of the join() method:

str.join(iterable)Code language: CSS (css)

The str will be the separator between elements in the result string.

If the iterable contains any non-string value, the join() method will raise a TypeError. To fix it, you need to convert non-string values to strings before calling the join() method.

The join() method has many practical applications. For example, you can use the join() method to compose a row for a CSV file.

Python string join examples #

Let’s take some examples of using the string join() method.

1) Using string join() method to concatenate multiple strings into a string #

The following example uses the string join() method to concatenate a tuple of strings without a separator:

colors = ('red', 'green', 'blue')
rgb = ''.join(colors)
print(rgb)Code language: PHP (php)

Output:

redgreenblue

The following example uses the string join() method with the comma separator (,):

colors = ('red', 'green', 'blue')
rgb = ','.join(colors)
print(rgb)Code language: PHP (php)

Output:

red,green,blue

2) Using string join() method to concatenate non-string data into a string #

The following example uses the join() method to concatenate strings and numbers in a tuple to a single string:

product = ('Laptop', 10, 699)
result = ','.join(product)
print(result)Code language: PHP (php)

Output:

TypeError: sequence item 1: expected str instance, int foundCode language: JavaScript (javascript)

It issued a TypeError because the tuple product has two integers.

To concatenate elements in the tuple, you’ll need to convert them into strings before concatenating. For example:

product = ('Laptop', 10, 699)
result = ','.join(str(d) for d in product)
print(result)Code language: PHP (php)

Output:

Laptop,10,699

How it works.

• First, use a generator expression to convert each element of the product tuple to a string.
• Second, use the join() method to concatenate the string elements

Summary #

• Use the join() method to concatenate multiple strings in an iterable into one string.