What are the differences between the concepts of generator and iterator in programming?

A generator is a special function that returns an iterator and allows sequential output of values using the yield keyword. An iterator is an object that implements the __next__() method and returns the next element of a sequence each time it is called.

Main differences:

• A generator creates an iterator automatically when called.
• An iterator is a more general interface that can be implemented manually in a class.
• Generators are convenient for lazy generation of sequences without the need to write a class.

Example of a generator:

def count_up_to(n):
    count = 1
    while count <= n:
        yield count
        count += 1

for num in count_up_to(5):
    print(num)

Here, count_up_to is a generator that returns numbers from 1 to n one at a time.