我在神经网络中经常用到这个。众所周知，当我们开始训练神经网络时，我们会随机初始化权重。该模型在特定数据集上的这些权重上进行训练。在数代之后，你得到了一组训练好的权重。

Now suppose you want to again train from scratch or you want to pass the model to others to reproduce your results, the weights will be again initialised to a random numbers which mostly will be different from earlier ones. The obtained trained weights after same number of epochs ( keeping same data and other parameters ) as earlier one will differ. The problem is your model is no more reproducible that is every time you train your model from scratch it provides you different sets of weights. This is because the model is being initialized by different random numbers every time.

如果每次你从头开始训练时，模型初始化到相同的随机初始化权重集会怎样?在这种情况下，您的模型可以变得可重复。这是通过numpy.random.seed(0)实现的。通过将seed()提到一个特定的数字，您将始终保留相同的随机数集。

想象一下，您正在向某人展示如何用一堆“随机”数字编写代码。通过使用numpy种子，它们可以使用相同的种子号并获得相同的“随机”数字集。

所以它不是完全随机的，因为算法会吐出数字但它看起来像是随机生成的一堆。

随机种子指定计算机生成随机数序列时的起始点。

For example, let’s say you wanted to generate a random number in Excel (Note: Excel sets a limit of 9999 for the seed). If you enter a number into the Random Seed box during the process, you’ll be able to use the same set of random numbers again. If you typed “77” into the box, and typed “77” the next time you run the random number generator, Excel will display that same set of random numbers. If you type “99”, you’ll get an entirely different set of numbers. But if you revert back to a seed of 77, then you’ll get the same set of random numbers you started with.

例如，“取一个数x，加上900 +x，然后减去52。”为了使进程开始，您必须指定一个起始数字x(种子)。让我们以77为例:

900 + 77 = 977 减去52 = 925 按照相同的算法，第二个“随机”数将是:

900 + 925 = 1825 减去52 = 1773 这个简单的例子遵循一个模式，但是计算机数字生成背后的算法要复杂得多

如果你每次调用numpy的其他随机函数时都设置np.random.seed(a_fixed_number)，结果将是相同的:

>>> import numpy as np
>>> np.random.seed(0) 
>>> perm = np.random.permutation(10) 
>>> print perm 
[2 8 4 9 1 6 7 3 0 5]
>>> np.random.seed(0) 
>>> print np.random.permutation(10) 
[2 8 4 9 1 6 7 3 0 5]
>>> np.random.seed(0) 
>>> print np.random.permutation(10) 
[2 8 4 9 1 6 7 3 0 5]
>>> np.random.seed(0) 
>>> print np.random.permutation(10) 
[2 8 4 9 1 6 7 3 0 5]
>>> np.random.seed(0) 
>>> print np.random.rand(4) 
[0.5488135  0.71518937 0.60276338 0.54488318]
>>> np.random.seed(0) 
>>> print np.random.rand(4) 
[0.5488135  0.71518937 0.60276338 0.54488318]

然而，如果你只调用它一次，并使用各种随机函数，结果仍然会不同:

>>> import numpy as np
>>> np.random.seed(0) 
>>> perm = np.random.permutation(10)
>>> print perm 
[2 8 4 9 1 6 7 3 0 5]
>>> np.random.seed(0) 
>>> print np.random.permutation(10)
[2 8 4 9 1 6 7 3 0 5]
>>> print np.random.permutation(10) 
[3 5 1 2 9 8 0 6 7 4]
>>> print np.random.permutation(10) 
[2 3 8 4 5 1 0 6 9 7]
>>> print np.random.rand(4) 
[0.64817187 0.36824154 0.95715516 0.14035078]
>>> print np.random.rand(4) 
[0.87008726 0.47360805 0.80091075 0.52047748]

如前所述，numpy.random.seed(0)将随机种子设置为0，因此从random获得的伪随机数将从同一点开始。在某些情况下，这有助于调试。然而，经过一些阅读，如果您有线程，这似乎是错误的方法，因为它不是线程安全的。

从differences-between-numpy-random-and-random-random-in-python:

For numpy.random.seed(), the main difficulty is that it is not thread-safe - that is, it's not safe to use if you have many different threads of execution, because it's not guaranteed to work if two different threads are executing the function at the same time. If you're not using threads, and if you can reasonably expect that you won't need to rewrite your program this way in the future, numpy.random.seed() should be fine for testing purposes. If there's any reason to suspect that you may need threads in the future, it's much safer in the long run to do as suggested, and to make a local instance of the numpy.random.Random class. As far as I can tell, random.random.seed() is thread-safe (or at least, I haven't found any evidence to the contrary).

如何做到这一点的例子:

from numpy.random import RandomState
prng = RandomState()
print prng.permutation(10)
prng = RandomState()
print prng.permutation(10)
prng = RandomState(42)
print prng.permutation(10)
prng = RandomState(42)
print prng.permutation(10)

可能给:

[3 0 4 6 8 2 1 9 7 5] [1 6 9 0 2 7 8 3 5 4] [8 1 5 0 7 2 9 4 3 6] [8 1 5 0 7 2 9 4 3 6]

最后，请注意，由于xor的工作方式，在某些情况下初始化为0(而不是所有位都为0的种子)可能会导致一些第一次迭代的不均匀分布，但这取决于算法，超出了我目前的担忧和这个问题的范围。

设置特定种子值后产生的所有随机数在所有平台/系统中都是相同的。