'numpy.ndarray' to 'str'

To convert a numpy ndarray to a string, you can use the `numpy.array2string()` function. Here's an example:

import numpy as np

arr = np.array([1, 2, 3])
arr_str = np.array2string(arr)

print(arr_str)

Output:

'[1 2 3]'

By default, `array2string()` separates the elements of the array with spaces and uses square brackets to enclose the array. You can modify this behavior by passing additional arguments to the function. For example, you can change the separator to a comma:

import numpy as np

arr = np.array([1, 2, 3])
arr_str = np.array2string(arr, separator=',')

print(arr_str)

Output:

'[1,2,3]'

You can also specify the precision of floating-point numbers and the indentation of the output. See the documentation for `array2string()` for more information on the available options.