Python String join()

Python String join() method

Python String join() method joins the strings in the given iterable by the separator string and returns the resulting string.

We call join() method on the separator string, and pass the strings to be joined as argument.

Syntax of join() method

The syntax of String join() method is

str.join(iterator)

where str is the separator string.

join() method takes one parameter.

For example, if str_1, str_2, and so on are the string items in the iterator, then the resulting string would be as shown in the following expression.

str_1 + str + str_2 + str + str_3 + ... + str_N

Return value

join() method returns a string value.

Exceptions

join() method raises TypeError exception if any of the items in the iterable is not a string, or if an iterable is not given as argument.

Examples

1. Join two strings with a space in Python

In this example, we will take two strings in str_1 and str_2, and join these strings with a single space.

str_1 = 'Hello'
str_2 = 'World'
result = ' '.join([str_1, str_2])
print(result)

Output

Hello World

2. Join strings in list with specific separator string in Python

In this example, we take a list my_list containing four strings, and join these strings with '--' string as separator.

my_list = ['apple', 'banana', 'cherry']
result = '--'.join(my_list)
print(result)

Output

apple--banana--cherry

3. Join strings in tuple in Python

In this example, we take a tuple with three string values, and join these strings with comma as separator.

Call join() method on comma string ',', and pass the set object as argument.

my_tuple = ('apple', 'banan', 'cherry')
result = ','.join(my_tuple)
print(result)

Output

apple,banan,cherry

4. Join strings in set in Python

In this example, we take some strings in a set, and join these strings with comma as separator.

Call join() method on comma string ',', and pass the set object as argument.

my_set = {'apple', 'banana', 'cherry', 'fig'}
result = ','.join(my_set)
print(result)

Output

fig,apple,cherry,banana

Since the items in a set are not ordered, we cannot guarantee the order of the strings. When you run the above program, the order of the strings in the resulting string may vary.

5. Stain join() method TypeError: sequence item 1: expected str instance, int found

In this example, we shall what happens if one of the items in the iterator (passed as argument to join() method) is not a string.

Let us take a list, where the second element is not a string, but an integer.

Call join() method on comma string ',', and pass the set object as argument.

my_list = ['apple', 25, 'cherry']
result = ','.join(my_list)
print(result)

Output

Traceback (most recent call last):
  File "/Users/pythonexamplesorg/main.py", line 2, in <module>
    result = ','.join(my_list)
             ^^^^^^^^^^^^^^^^^
TypeError: sequence item 1: expected str instance, int found

Therefore, we have to make sure that the items in the given argument iterator are of only string type.

Summary

In this tutorial of Python String Methods, we learned about String lower() method, its syntax, and how to use this method to join strings with various examples.