Basics



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class Number:
    def __init__(self, start):
        self.data = start
    def __sub__(self, other):
        return Number(self.data - other)



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X = Number(5)
Y = X - 3
Y.data

Indexing and slicing



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class Indexer:
    def __getitem__(self, index):
        return index ** 2



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X = Indexer()
X[2]



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for i in range(5):
    print(X[i], end=' ')

Intercepting the Slices



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L = [5, 6, 7, 8, 9]



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L[2:4]



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L[1:]



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L[:-1]



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L[::2]



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L[slice(2, 4)]



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L[slice(1, None)]



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L[slice(None, -1)]



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L[slice(None, None, 2)]



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class Indexer:
    data = [5, 6, 7, 8, 9]
    def __getitem__(self, index):
        print('getitem: ', index)
        return self.data[index]



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X = Indexer()



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X[0]



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X[1]



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X[-1]



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X[2:4]



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X[1:]



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X[:-1]



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X[::2]



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class Indexer:
    def __getitem__(self, index):
        if isinstance(index, int):
            print('indexing', index)
        else:
            print('slicing', index.start, index.stop, index.step)



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X = Indexer()
X[99]



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X[1:99:2]



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X[1:]

Index iteration



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class StepperIndex:
    def __getitem__(self, i):
        return self.data[i]



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X = StepperIndex()
X.data = 'Spam'
X[1]



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for item in X:
    print(item, end=' ')



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'p' in X



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[c for c in X]



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list(map(str.upper, X))



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(a, b, c, d) = X
a, c, d



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list(X), tuple(X), ' '.join(X)



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X



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