In today’s Data Analysis tutorial we’ll solve a common issue that you might have encountered when trying to add new elements to a Numpy array.
Reproducing the error
Let’s see together how we can easily reproduce the error:
# import the numpy library
import numpy as np
#create a short numpy array
my_array = np.arange(10, 110, 10)
#print the array
print(my_array)This will return the following ndarray object:
[ 10 20 30 40 50 60 70 80 90 100]
Next we would like to add a couple of new elements of a list to the array. W e will try to use the append method:
my_array.append([120, 130])This will fail with the following attribute error exception, screenshot taken from my Jupyter notebook (you will get the same error in PyCharm, VS COde, Spyder, Colab etc’):
Fix the attribute error no append in Numpy
As we saw above, we tried to use the Python append method on a numpy array. Append is used with Python lists, and is not available for numpy arrays.
You are able to get rid of the error in multiple ways:
- Using np.append to concatenate the list to the numpy array
my_array = np.append(my_array, [120, 130])- Convert the list to an array and append
my_new_array = np.array([120,130])
my_array = np.append(my_array, my_new_array)- Using np.concatenate
my_new_array = np.array([120,130])
my_array = np.concatenate((my_array, my_new_array))All the above will render the same result – in our case, the following numpy array:
array([ 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 130])