Numpy Array Assignment: Memory Allocation Differences

In NumPy, there are three common ways to assign values to an array:

• B = A
• B[:] = A
• numpy.copy(B, A)

B = A

When you use B = A, you are not creating a new array. Instead, you are binding a new name (B) to the existing array (A). As a result, any modifications made to one array will be reflected in the other.

B[:] = A

This syntax creates a new array B with the same dimensions and values as A. The original array A is not modified. This method requires less memory allocation compared to numpy.copy.

numpy.copy(B, A)

This method is not legal as you have it written. It should be B = numpy.copy(A). numpy.copy creates a new array B with the same dimensions and values as A. This method requires more memory allocation compared to B[:] = A because it creates a separate physical copy of the data from the original array.

When is Additional Memory Allocated?

Additional memory is allocated when you use numpy.copy to create a new physical copy of the array. This is because it allocates a new contiguous block of memory for the copied data.

When is Memory Not Allocated?

Memory is not allocated when you use B = A because you are simply renaming the original array. Memory is also not allocated when you use B[:] = A because it reuses the same memory location as the original array.