advancedAdvanced Topics

Generators & Iterators

Create memory-efficient iterables with yield and iterator protocol.

In this lesson

01Generator Functions
02Iterator Protocol

01Generator Functions

Use yield to produce a sequence of values lazily, one at a time.

Python

1def countdown(n):
2    while n > 0:
3        yield n
4        n -= 1
5
6for num in countdown(5):
7    print(num, end=" ")

Output

5 4 3 2 1

02Iterator Protocol

Implement __iter__ and __next__ to create custom iterable objects.

Python

1class Counter:
2    def __init__(self, start, end):
3        self.current = start
4        self.end = end
5    
6    def __iter__(self):
7        return self
8    
9    def __next__(self):
10        if self.current > self.end:
11            raise StopIteration
12        val = self.current
13        self.current += 1
14        return val
15
16for n in Counter(1, 5):
17    print(n, end=" ")

Output

1 2 3 4 5

Decorators

Context Managers