Python String Join – With Examples

In python, the string join method, join(), is used to combine all the items of an iterable (example – list, tuple, set, etc.) into a single string separated by a separator.

ls = ["I", "like", "coding", "in", "python"]
print(" ".join(ls))

Output:

I like coding in python

Table of Contents

• Syntax
• Examples

Syntax

The following syntax is used to apply the string join function in python.

string.join(iterable)

Note: The string in the above syntax refers to the string separator to use for joining the items in the iterable.

Parameters:

The join() function takes an iterable as its parameter. Iterable are objects capable of returning its member one at a time. List, tuple, set, dictionary, string, etc are all iterable objects.

Returns:

A string resulting from the concatenation of the elements of the iterator and separated by the separator string passed.

Note: A TypeError exception is raised if the iterator contains any non-string values.

Examples:

Example 1: Joining elements of a list

ls = ['a', 'b', 'c', 'd']
print("The iterable to join:", ls)
# Using a single space as a separator
print("Join using single space:", " ".join(ls))
# Using an empty string as a separator
print("Join using empty string:", "".join(ls))

Output:

The iterable to join: ['a', 'b', 'c', 'd']
Join using single space: a b c d
Join using empty string: abcd

In the above example, we see that the elements of the list are joined using the separator string provided.

Example 2: When the iterable contains a non-string value

ls = ['a', 1, 'b', 'c', 'd']
# Using a single space as a separator
print("Join using single space:", " ".join(ls))

Output:

TypeError                                 Traceback (most recent call last)
<ipython-input-6-5f89fa28c958> in <module>
      1 ls = ['a', 1, 'b', 'c', 'd']
      2 # Using a single space as a separator
----> 3 print("Join using single space:", " ".join(ls))

TypeError: sequence item 1: expected str instance, int found

In the above example, a TypeError is raised as the iterable contained a non-string value.

Example 3: Joining elements of a tuple

tup = ('a', 'b', 'c', 'd')
print("The iterable to join:", tup)
# Using a single space as a separator
print("Join using single space:", " ".join(tup))
# Using an empty string as a separator
print("Join using underscore:", "_".join(tup))

Output:

The iterable to join: ('a', 'b', 'c', 'd')
Join using single space: a b c d
Join using underscore: a_b_c_d

Tuples are also iterable and hence the join function is able to concatenate its element into a single string using the separator provided.

Example 4: Joining elements of a set

set1 = {'a', 'b', 'c', 'd'}
# Using a single space as a separator
print("Join using comma:", ",".join(set1))

Output:

Join using comma: a,b,d,c

In the above example, the elements of the set have been joined using the separator , but the order is not the same as in the set we initialized. This is because a set is an unordered collection so you may get different sequences in output when working with sets.

Example 5: Joining elements of a dictionary

sample_dict = {'a': 1, 'b': 2, 'c': 3, 'd': 4}
print(", ".join(sample_dict))

Output:

a, b, c, d

In the above example, we see that when joining a dictionary, its keys are joined together and not the values. If a dictionary has a non-string key, a TypeError exception will be raised if you try to join it using the string join() function.

For more on the join function refer to the python docs.