Python String join() Method

The join() method in Python is used to concatenate the elements of an iterable (such as a list, tuple, or set) into a single string with a specified delimiter placed between each element.

Lets take a simple example to join list of string using join() method.

Joining a List of Strings

In below example, we use join() method to combine a list of strings into a single string with each string separated by a space.

a = ['Hello', 'world', 'from', 'Python']
res = ' '.join(a)
print(res)  

Hello world from Python

Syntax of join()

separator.join(iterable)

Parameters:

• separator: The string placed between elements of the iterable.
• iterable: A sequence of strings (e.g., list, tuple etc) to join together.

Return Value:

• Returns a single string formed by joining all elements in the iterable, separated by the specified separator
• If the iterable contains any non-string values and it raises a TypeError exception.

Examples of join() Method on Different Data Types

Below are examples of how join() method works with different data types.

Using join() with Tuples

The join() method works with any iterable containing strings, including tuples.

s = ("Learn", "to", "code")
# Separator "-" is used to join strings
res = "-".join(s)
print(res)

Learn-to-code

Using join() with set

In this example, we are joining set of String.

s = {'Python', 'is', 'fun'}
# Separator "-" is used to join strings
res = '-'.join(s)
print(res) 

Python-is-fun

Note: Since sets are unordered, the resulting string may appear in any order, such as "fun is Python" or "Python is fun".

Using join() with Dictionary

When using the join() method with a dictionary, it will only join the keys, not the values. This is because join() operates on iterables of strings and the default iteration over a dictionary returns its keys.

d = {'Geek': 1, 'for': 2, 'Geeks': 3}
# Separator "_" is used to join keys into a single string
res = '_'.join(d)
print(res)

Geek_for_Geeks