Difference among Iterable, Iterator and Generator

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What's Iterable, Iterator, Generator in Python?

Iterable(metaclass=ABCMeta)

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"""
__iter__
"""

@abstractmethod
def __iter__(self):
    while False:
        yield None

@classmethod
def __subclasshook__(cls, C):
    if cls is Iterable:
        return _check_methods(C, "__iter__")
    return NotImplemented

Iterator(Iterable)

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"""
__next__
"""

@abstractmethod
def __next__(self):
    'Return the next item from the iterator. When exhausted, raise StopIteration'
    raise StopIteration

def __iter__(self):
    return self

@classmethod
def __subclasshook__(cls, C):
    if cls is Iterator:
        return _check_methods(C, '__iter__', '__next__')
    return NotImplemented

Generator(Iterator)

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"""
send()
throw()
close()
"""

def __next__(self):
    """Return the next item from the generator.
    When exhausted, raise StopIteration.
    """
    return self.send(None)

@abstractmethod
def send(self, value):
    """Send a value into the generator.
    Return next yielded value or raise StopIteration.
    """
    raise StopIteration

@abstractmethod
def throw(self, typ, val=None, tb=None):
    """Raise an exception in the generator.
    Return next yielded value or raise StopIteration.
    """
    if val is None:
        if tb is None:
            raise typ
        val = typ()
    if tb is not None:
        val = val.with_traceback(tb)
    raise val

def close(self):
    """Raise GeneratorExit inside generator.
    """
    try:
        self.throw(GeneratorExit)
    except (GeneratorExit, StopIteration):
        pass
    else:
        raise RuntimeError("generator ignored GeneratorExit")

@classmethod
def __subclasshook__(cls, C):
    if cls is Generator:
        return _check_methods(C, '__iter__', '__next__',
                              'send', 'throw', 'close')
    return NotImplemented

Conclusion

Generator is Iterator.

Iterator is Iterable.

According to __subclasshook__ function,

Iterable, must implement __iter__

Iterator, must implement __iter__ and __next__

Generator, must implement __iter__ , __next__, send, throw and close