Python · Generators & Iterators

What does this print? class Count: def init(self, n): self.n, self.i = n, 0 def iter(self): return self def next(self): if self.i >= self.n: raise StopIteration self.i += 1 return self.i c = Count(2) for a in c: for b in c: print(a, b)

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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) ```

What is the key difference in behavior between [x for x in big] and (x for x in big)?

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? class Count: def __init__(self, n): self.n, self.i = n, 0 def __iter__(self): return self def __next__(self): if self.i >= self.n: raise StopIteration self.i += 1 return self.i c = Count(2) for a in c: for b in c: print(a, b)

More in Generators & Iterators

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What does this print? class Count: def init(self, n): self.n, self.i = n, 0 def iter(self): return self def next(self): if self.i >= self.n: raise StopIteration self.i += 1 return self.i c = Count(2) for a in c: for b in c: print(a, b)