Python 常识入门(?)

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[i for i in range(10)]
(i for i in range(10))
{i for i in range(10)}
{i:i for i in range(10)}

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lambda arguments : expression

x = lambda a : a + 10
print(x(5))

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arr=[1,8,3,6,5,4,7,2,9]

sorted(arr)
list.sort(reverse=True|False, key=myFunc)

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def myFunc(e): 
    return e['year']

cars = [
  {'car': 'Porsche', 'year': 1963},
  {'car': 'Audi', 'year': 2010},
  {'car': 'BMW', 'year': 2019},
  {'car': 'Volvo', 'year': 2013}
]

cars.sort(key=myFunc)
cars.sort(key=lambda e: e['year'])

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from functools import lru_cache
@lru_cache(None)
def add(x, y):
    print("calculating: %s + %s" % (x, y))
    return x + y
add.clear_cache()
print(add(1, 2))
print(add(1, 2))
print(add(2, 3))

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>>> a=5;id(a)
2094838213040
>>> a=6;id(a)
2094838213072

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>>> arr=[1,2,3];id(arr)
2094872788160
>>> arr[2]*=-1;id(arr)
2094872788160

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>>> arr=[[0]*5 for i in range(2)];arr
[[0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]
>>> arr[1][1]=1;arr
[[0, 0, 0, 0, 0], [0, 1, 0, 0, 0]]

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>>> arr=[[0]*5]*2;arr
[[0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]
>>> arr[1][1]=1;arr
[[0, 1, 0, 0, 0], [0, 1, 0, 0, 0]]