Python Iterators

1) Convert List to Iterator

Take a list [1,2,3], convert it to an iterator using iter(), and print each value using next().

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2) Loop with Iterator

Use iter() on a list and loop through values using while + next() until StopIteration.

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3) String Iterator

Create an iterator from a string "python" and print each character.

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4) Tuple Iterator

Convert a tuple (10,20,30) to an iterator and print all items.

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5) Dictionary Iterator

Iterate over a dictionary’s keys using iter() and next().

Example:

d = {"a":1, "b":2}

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6) Iterate Over Values

Iterate values of a dictionary using iter() and next().

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7) Zip Iterator

Use zip() on two lists and iterate the resulting iterator to print pairs.

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8) Iterator With For Loop

Use iter() to create an iterator from a list, then loop with for to print elements.

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9) StopIteration in Try/Except

Convert a list to an iterator. Use next() more times than elements and catch StopIteration.

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10) Custom Iterator Class (Basic)

Create a class with __iter__() and __next__() that yields numbers 1–5.

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11) Iterator That Squares

Modify #10 so the iterator yields squares: 1,4,9,16,25.

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12) Infinite Iterator (Safely)

Create a class iterator that yields even numbers starting from 0. Stop after 10 items.

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13) Iterator From Range

Use iter(range(1,6)) and print using next().

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14) Iterator With Condition

Create an iterator that yields only even numbers from [1,2,3,4,5,6].

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15) Convert Iterable to List

Use iterator + list() to convert an iterable into a list.

Example:

it = iter("abc")

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16) Nested Iterators

Create two iterators (list & string) and print pairs using nested loops.

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17) Chaining Iterators

Use itertools.chain() to combine two lists and iterate.

(Import itertools first.)

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18) Filter Iterator

Use itertools.filterfalse() to skip even numbers from a list iterator.

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19) Take While Iterator

Use itertools.takewhile() to take numbers < 5 from a list iterator.

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20) Custom Iterator With Reset Method

Extend a class iterator so it has a .reset() method that starts iteration over again.

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🧠 Key Concepts Practiced

Concept	What You Practice
Creating an iterator	iter() on lists, strings, etc.
Consuming an iterator	next()
Handling end of iteration	catching StopIteration
Building your own iterator	implementing __iter__ & __next__
Iterator utilities	with itertools

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📌 Mini Example

Simple iterator with next()

nums = [10,20,30]
it = iter(nums)

print(next(it))  # 10
print(next(it))  # 20
print(next(it))  # 30

Basic custom iterator

class MyIter:
    def __init__(self):
        self.num = 1

    def __iter__(self):
        return self

    def __next__(self):
        if self.num <= 5:
            val = self.num
            self.num += 1
            return val
        else:
            raise StopIteration

it = MyIter()
for n in it:
    print(n)

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canvil: 333f6c7d-6876-4f7e-b6ad-1bdb2233f5c1