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Why is it string.join(list) instead of list.join(string) in Python?

Last Updated : April 27, 2025

In Python, string.join(list) is used because the string defines the separator, making it responsible for joining the list elements together.

The join() is a string method and while using it the separator string iterates over an arbitrary sequence, forming string representations of each of the elements, inserting itself between the elements.

Why join() Is a String Method and Not a List Method in Python

Concisely, it's because join and string.join() are both generic operations that work on any iterable and is a string method.

Because it is a string method, the join() can work for the Unicode string as well as plain ASCII strings.

Example 1: Joining List Elements with a String Separator

test_string = "test"
result = test_string.join(["1", "2", "3", "4"])
print(result)

The output of the above code will be:

1test2test3test4

Explanation

In the above example, the string "test" is joined between every element of the list ["1", "2", "3", "4"].

Example 2: Using join() with a String

# Define the string
test_string = "test"

# Use the join method with a string
result = test_string.join("---")

# Print the result
print(result)

The output of the above code will be:

-tteste-ttest-

Exercise

Select the correct option to complete each statement about why Python uses string.join(list) instead of list.join(string).

1. The join() method is called on the ___ that will appear between list elements. --Select-- separator string list character
2. In Python, lists do not have a ___ method because the join operation conceptually belongs to strings. --Select-- concatenate join split
3. The join() method returns a single ___ after joining all list elements. --Select-- string list tuple