NumPy random.shuffle function

Question

I ran into something strange with numpy.random.shuffle function

from numpy import arange
from numpy.random import shuffle

a = arange(5)
b = a
c = a[:]

shuffle(c)

a and b all changes with c. Actually no matter I shuffle() which variable, the other two all changes with it. I thought when I use slice copy the original variable should be independent. Did I miss something? How can I protect the original variable from being changed?

Using a slice makes a copy for ordinary lists, but not necessarily for all types. You have to read the documentation for any kind of object to use to see if slicing makes a copy or not. — BrenBarn
– BrenBarn, Commented Jul 14, 2013 at 7:27

falsetru · Accepted Answer · 2013-07-14 07:20:46Z

5

According to the Basic slicing documentation:

All arrays generated by basic slicing are always views of the original array.

Use ndarray.copy or numpy.copy to get copy.

edited Jul 14, 2013 at 7:20

answered Jul 14, 2013 at 7:10

falsetru

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Comments

Saullo G. P. Castro · Accepted Answer · 2014-05-08 20:02:45Z

1

Using c = a.copy() can help you.

edited May 8, 2014 at 20:02

Saullo G. P. Castro

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answered Jul 14, 2013 at 7:10

zhangyangyu

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