next(iterator) function is one of Python’s built-in functions—so, you can use it without importing any library. It returns the next value from the
iterator you pass as a required first argument. An optional second argument
default returns the passed default value in case the iterator doesn’t provide a next value.
- iterator – the next element is retrieved from the
- default (optional) – return value if iterator is exhausted (it doesn’t have a next element)
Example 1: No Default Value
The following example shows the
next() function in action—without using a default value in case the iterator is empty.
users = ['Alice', 'Bob', 'Carl', 'David'] # convert the list to an iterator users_iterator = iter(users) x = next(users_iterator) print(x) # Output: 'Alice' x = next(users_iterator) print(x) # Output: 'Bob' x = next(users_iterator) print(x) # Output: 'Carl' x = next(users_iterator) print(x) # Output: 'David'
Each time you call
next(iterator), the iterator returns the next element in the iterator over the Python list
But what happens if you call the
next() function once more on the now empty
x = next(users_iterator) print(x) ''' Traceback (most recent call last): File "C:\Users\xcent\Desktop\Finxter\Blog\HowToConvertBooleanToStringPython\code.py", line 22, in <module> x = next(users_iterator) StopIteration '''
Python throws a
Let’s learn how to fix this!
Example 2: With Default Value
Not providing Python a solution to the problem that the iterator may be empty is a common source of errors! You can fix the errors by passing the optional
x = next(users_iterator, 42) print(x) # 42
Now, you cannot crash the
next(...) function anymore! Go ahead and try it…
The interactive code shell offers you a way to try your newly gained skill—understanding the
next() function. Can you crash the script by changing the function arguments?
Exercise: Run the code in the interactive shell. Now, change the default value & run again!
Where to Go From Here?
Enough theory. Let’s get some practice!
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If you just want to learn about the freelancing opportunity, feel free to watch my free webinar “How to Build Your High-Income Skill Python” and learn how I grew my coding business online and how you can, too—from the comfort of your own home.
While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students.
To help students reach higher levels of Python success, he founded the programming education website Finxter.com that has taught exponential skills to millions of coders worldwide. He’s the author of the best-selling programming books Python One-Liners (NoStarch 2020), The Art of Clean Code (NoStarch 2022), and The Book of Dash (NoStarch 2022). Chris also coauthored the Coffee Break Python series of self-published books. He’s a computer science enthusiast, freelancer, and owner of one of the top 10 largest Python blogs worldwide.
His passions are writing, reading, and coding. But his greatest passion is to serve aspiring coders through Finxter and help them to boost their skills. You can join his free email academy here.