Iterators and Context Managers

Iterators

An iterator is an object that implements the __iter__() and __next__() methods, allowing traversal through elements one at a time.

Example of an Iterator

class Counter:
    def __init__(self, start, end):
        self.current = start
        self.end = end
    
    def __iter__(self):
        return self
    
    def __next__(self):
        if self.current > self.end:
            raise StopIteration
        value = self.current
        self.current += 1
        return value

# Using the iterator
counter = Counter(1, 5)
for num in counter:
    print(num)

Output:

1
2
3
4
5

Context Managers

A context manager is an object that properly manages resources using the with statement. It ensures resources (like files, network connections) are released properly after use.

Example of a Context Manager using with

class FileManager:
    def __init__(self, filename, mode):
        self.filename = filename
        self.mode = mode

    def __enter__(self):
        self.file = open(self.filename, self.mode)
        return self.file

    def __exit__(self, exc_type, exc_value, traceback):
        self.file.close()

# Using the context manager
with FileManager("example.txt", "w") as file:
    file.write("Hello, world!")

# The file is automatically closed outside the `with` block.