Python · Generators & Iterators

What does this print, and why is defining iteration this way convenient? class Countdown: def init(self, n): self.n = n def iter(self): for i in range(self.n, 0, -1): yield i print(list(Countdown(3)))

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What does this print? ``` gen = (x*x for x in range(3)) print(sum(gen)) print(sum(gen)) ```

What does calling this line do? ``` def squares(n): for i in range(n): yield i*i g = squares(3) ```

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What does this print? ``` i = iter([10, 20]) print(next(i, 'done')) print(next(i, 'done')) print(next(i, 'done')) ```

Which methods must an iterator implement, and what ends the iteration?

An iterator's __next__ has run out of items. How does it signal "no more"?

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What does this print, and why is defining iteration this way convenient? class Countdown: def __init__(self, n): self.n = n def __iter__(self): for i in range(self.n, 0, -1): yield i print(list(Countdown(3)))

More in Generators & Iterators

Start learning today

What does this print, and why is defining iteration this way convenient? class Countdown: def init(self, n): self.n = n def iter(self): for i in range(self.n, 0, -1): yield i print(list(Countdown(3)))