When we implement our own obj in python which support for i in obj statement, what magic method we need to create?
Is there a link to the official document that I can check?
During my reading of some other's source code, I found there's a __getitem__ method, it has a signatue of __getitem__(slef, index), then when we instantiate an object of this class, and call
for i in obj: print(i) what method would python try to find and pass what argument?
You can make a class iterable by implementing
__getitem, it'll receive ints starting at 0, your code needs to raise a IndexError to stop it
class Foo: def __getitem__(self, item): if isinstance(item, int) and item > 10: raise IndexError return item * 2 __iter__ and __next__
class Foo: def __init__(self): self.counter = 0 def __iter__(self): return self def __next__(self): if self.counter > 10: raise StopIteration result = self.counter * 2 self.counter += 1 return result Both leads to same output
for i in Foo(): print(i) 0 2 4 6 8 10 12 14 16 18 20 