[numpy]random.choice()隨機選取內容

讀代碼看到這句

    np.random.choice([i for i in images[:200] if not is_empty(i)], size = 8)

https://www.kaggle.com/rackovic1994/convolutional-neural-network

概述：

可以從一個int數字或1維array裏隨機選取內容，並將選取結果放入n維array中返回。

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說明：

numpy.random.choice(a, size=None, replace=True, p=None)

a : 1-D array-like or int
    If an ndarray, a random sample is generated from its elements. 
    If an int, the random sample is generated as if a was np.arange(n)

size : int or tuple of ints, optional 

replace : boolean, optional
    Whether the sample is with or without replacement

p : 1-D array-like, optional
    The probabilities associated with each entry in a. If not given the sample assumes a uniform distribution over all entries in a.

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示例

>>> np.random.choice(5, 3)
array([0, 3, 4])

>>> np.random.choice(5, 3, p=[0.1, 0, 0.3, 0.6, 0])
array([3, 3, 0])

>>> np.random.choice(5, 3, replace=False)
array([3,1,0])

>>> np.random.choice(5, 3, replace=False, p=[0.1, 0, 0.3, 0.6, 0])
array([2, 3, 0])

>>> aa_milne_arr = ['pooh', 'rabbit', 'piglet', 'Christopher']

>>> np.random.choice(aa_milne_arr, 5, p=[0.5, 0.1, 0.1, 0.3])
array(['pooh', 'pooh', 'pooh', 'Christopher', 'piglet'],

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官方介紹

http://docs.scipy.org/doc/numpy-dev/reference/generated/numpy.random.choice.html

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感謝 https://blog.csdn.net/autoliuweijie/article/details/51982514