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.
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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.
Other articles on python strings:
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