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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Practice projects is how you sharpen your saw in coding!
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Then become a Python freelance developer! It’s the best way of approaching the task of improving your Python skills—even if you are a complete beginner.
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