Understanding Python String join()

In Python, String join() is an inbuilt function that is used to return the result when a string is concatenated with an iterable like list , tuple, dictionary, set, etc.

• With this join(), function any string can be concatenated flexibly.
• Basically with this function, every single element of an iterable (like list, tuple, dictionary, set, etc) gets concatenated with the string and the concatenated string is returned as a result.
• If there is a non-string value in an iterable then TypeError exception will be raised.
• Also Python String join() method is the method that is used to return the string in which the elements of any sequence have been joined by using string separator.

Below we have a basic syntax of String join() in Python:

string.join(iterable)

Python String **join()**: parameters

iterable ( It is an object whose all values are returned in the form of a string); is a parameter of join() function of Python Strings. It has some values and these are given below:

• list
• string
• tuple
• dictionary
• set

Python String **join()**: Return Value

• Whenever non-string values are there in an iterable then TypeError exception will be raised.
• Whenever a dictionary is used as an iterable, then returned values are the keys, not the values.
• Whenever string values are there in an iterable concatenated string that is returned as a result.

Here we are going to define a tuple with its element and then after we will join by using .join() function:

fruits= ('Mango', 'Apple', "Orange")
str = '|'.join(fruits)
print(str)

In the above example we have first defined a tuple and then join that tuple values with the | as you can see the output below:

Mango|Apple|Orange

In the python script below, we have tried using the join() function with a list ( A data structure in Python is a mutable/changeable, ordered sequence of elements) as an iterable:

x = ['WonderWoman', 'Aquaman', 'Batman', 'Superman']
movies = '||'.join(x)
print(movies)

In the above example we have first defined a list and then join that list values with the || as you can see the output below:

WonderWoman||Aquaman||Batman||Superman

In the python script below, we have tried using the join() function with a dictionary ( Unordered collection of data values; It holds the key: value pair) as an iterable:

technologies = {
    1: 'AI',
    2: 'Machine Learning',
    3: 'Serverless',
    4: 'ARVR'
}
trends= '/'.join(technologies.values())
print(trends)

In the above example, we have used dictionary values and join them with a separator /. The output for the same is given below:

AI/Machine Learning/Serverless/ARVR

In the python script below, we have tried using the join() function with a set ( a collection of elements which is unordered and unindexed) as an iterable:

a=  {'11', '21', '29'}
bc = ', '
print(bc.join(a))

In the above example, we have used a set and join them with a separator , .As set is unordered so you will see elements in a different order in the output. The output for the same is given below:

29, 11, 21

Whenever non-string values are there in an iterable then TypeError exception will be raised. Let us see this with the help of an example given below:

a=(11,21)
b='/'
print(b.join(a))

Here we have the output for the same:

Traceback (most recent call last): File "<pyshell#18>", line 1, in <module> print(b.join(a)) TypeError: sequence item 0: expected str instance, int found

In this tutorial, we learned join() method of Strings in Python that is used to return the result when a string is concatenated with an iterable. We also saw its parameters and returned values; we had used different iterables like list,set,tuple dictionary in our examples also followed by a Live Example.