Author | Logan Chien

  1. Item 8: Lexical Scope

    def f(x):
    if x <= 1:
        return x
    return f(x - 1) + f(x - 2)

g = f

def f(x):
    return x

print(f(23))
print(g(23))

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  2. Item 7: Generator Function

    from itertools import dropwhile, takewhile, islice

def fibs():
    a, b = 0, 1
    while True:
        yield a
        a, b = b, a + b

for x in fibs():
    print(x)
    if x > 250:
        break

print(list(islice(fibs(), 15)))
print(list(takewhile(lambda x: x < 250, \
           dropwhile(lambda x: x < 8, fibs()))))

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  3. Item 6: Generator Expression

    a = [x * 2 for x in range(5)]
b = (x * 2 for x in range(5))

print('a=', a)
print('b=', b)

for t in range(2):
    # Run Following Code Twice

    print('----')
    for i, x in enumerate(a):
        print('a[{}]={}'.format(i, x))

    print('----')
    for i, x in enumerate(b …

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  4. Item 5: Method Resolution Order

    class A(object):
    def __init__(self):
        print('A', end='')
class B(A):
    def __init__(self):
        super().__init__()
        print('B', end='')
class C(A):
    def __init__(self):
        super().__init__()
        print('C', end='')
class D(B, C):
    def __init__(self):
        super().__init__()
        print('D', end='')
A(); print();  B(); print();
C(); print();  D …

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  5. Item 4: Default Arguments

    def append_x(x, a=None, b=None, c=[]):
    a = a or []
    b = b if b is not None else []
    a.append(x)
    b.append(x)
    c.append(x)
    print(a, b, c)

s, t, u = [], [], []
append_x(1)
append_x(2, s, t)
append_x(3, s, t, u)
print(s, t, u …

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  7. Item 2: for while else

    def foo(xs):
    for i in xs:
        if i % 5 == 0:
            print('found', i)
            break
    else:
        print('not found')
if __name__ == '__main__':
    foo([])
    foo([3, 4])
    foo([4, 5, 6])

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