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Copy array by value and reference in NumPy

In this article, we will see the difference between copying an array by values and by reference.

Copy by reference

If you copy an array by reference, then it means that change in value of one array will also change the value of other array.

Consider the following example

 import numpy as np

arr = np.arange(0,10)

# Copy by reference
arr_ref = arr

# Printing array
print("Arr:", arr, ",  arr_ref:", arr_ref)

# Change in value of arr
arr[:] = 20

# Printing array
print("Arr:", arr, ",  arr_ref:", arr_ref)

In this example

   1. We have 2 arrays i.e. arr and arr_ref.

   2. The reference of arr is copied to arr_ref.

   3. Change in value of arr is also reflected in arr_ref..

Here is the output of the above program.

Click to Enlarge

Copy by value

Copy by value means, you are only copying values and change in one array does not impact the value in another array.

You can use copy function to copy the value of one array to another. Consider the following example

 import numpy as np

arr = np.arange(0,10)

# Copy by values
arr_ref = arr.copy()

# Printing array
print("Arr:", arr, ",  arr_ref:", arr_ref)

# Change in value of arr
arr[:] = 20

# Printing array
print("Arr:", arr, ",  arr_ref:", arr_ref)

In the above code, we are copying by value. Once you run the above code, you will get following output

Click to Enlarge

Posted By -	Karan Gupta

Posted On -	Thursday, March 28, 2019

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