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How to make a NumPy array read-only?
  • Last Updated : 29 Aug, 2020

Let’s discuss how to make NumPy array immutable i.e that can not be rewritten or can’t be changed. This can be done by setting a writeable flag of the NumPy array to false.

Syntax:

array.flags.writeable=False

 This set the writable flag to false and hence array becomes immutable i.e read-only. See the example below

Example:

Python






import numpy as np
  
  
a = np.zeros(11)
print("Before any change ")
print(a)
  
a[1] = 2
print("Before after first change ")
print(a)
  
a.flags.writeable = False
print("After making array immutable on attempting  second change ")
a[1] = 7

Output:

Before any change
[0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.]
Before after first change
[0. 2. 0. 0. 0. 0. 0. 0. 0. 0. 0.]
After making array immutable on attempting  second change
Traceback (most recent call last):
  File "gfg9.py", line 11, in <module>
    a[1]=7
ValueError: assignment destination is read-only

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