numpy.random.choice 中replace 的含义

numpy.random.choice的官方定义见这里

搬运过来如下：

numpy.random.choice(a, size=None, replace=True, p=None)
Generates a random sample from a given 1-D array
New in version 1.7.0.

Parameters:

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

Output shape. If the given shape is, e.g., (m, n, k), then m * n * k samples are drawn. Default is None, in which case a single value is returned.

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.

Returns:

samples : 1-D ndarray, shape (size,)
The generated random samples

Raises:

ValueError
If a is an int and less than zero, if a or p are not 1-dimensional, if a is an array-like of size 0, if p is not a vector of probabilities, if a and p have different lengths, or if replace=False and the sample size is greater than the population size

用人话简单解释一下：

从一维 数组 a 中选出 size 个元素，a中每个元素被选中的概率由一维数组p定义。

可replace是什么鬼？（每个官方解释单词都能看懂，就是不懂在说什么。。）
查了一下，原文见stackoverflow.

简单解释一下：

replace=True: 可以从a 中反复选取同一个元素。
replace=False: a 中同一个元素只能被选取一次。

搬运栗子：

from numpy import random as rdary = list(range(10))# usageIn[18]: rd.choice(ary, size=8, replace=False)Out[18]: array([0, 5, 9, 8, 2, 1, 6, 3])  # no repeated elementsIn[19]: rd.choice(ary, size=8, replace=True)Out[19]: array([4, 9, 8, 5, 4, 1, 1, 9])  # elements may be repeated