Valueerror: Need at Least One array to Concatenate ( Solved )

As a Python programmer you may get the error like ValueError: need at least one array to concatenate. Due to this, it may be time-consuming. In this tutorial you will know how to solve the Valueerror: Need at Least One array to Concatenate error easily. You will know the various causes of it.

What is concatenate in Python?

In Python concatenation is a process of appending one array to another array. For example, if you have an array1 = [1,2,3]and array2 = [4,5,6 ]and want to concatenate array2 to array1 then you will use some specific function. The final output will be array 1  =[1,2,3,4,5,6].

What causes Valueerror: Need at Least One array to Concatenate Error?

Let’s know all the causes for this value error.

Cause 1: Empty Arrays

The main cause for getting this error is that you must be concatenating the two arrays that are empty. The Python interpreter will raise the error when you try to do this.

You will get the error when you run the below lines of code.

import numpy as np
arr1 = np.array([])
arr2 = np.array([])
np.concatenate((arr1, arr2))

Output

Valueerror: need at least one array to concatenate

Cause 2: Concatenating one array with an empty array

The other cause that encounters this error is that you must be concatenating one array with the other empty error.

Run the below lines of code and see you will get the error.

import numpy as np
arr1 = np.array([])
arr2 = np.array([1,2,3])
np.concatenate((arr1, arr2))

Output

Valueerror: need at least one array to concatenate

Cause 3: Array is not defined

There may be a case when you try to concatenate one array with another array that is not defined yet. Due to this, you get the error.

Cause 4: Dimensions not matched

You can also get the error when you are trying to concatenate the arrays whose dimensions are not matched. If any one of the array is of different shapes or sizes then it will raise the ValueError.

Solution of Need at Least One array to Concatenate

The above were the causes of the error. Now let’s find the solution to it.

Solution 1: Check Empty Array

The first solution is that you must check whether any one of the arrays is empty or not. If it is not then concatenate otherwise not.

You will not get the error when you will run the below lines of code.

import numpy as np

arr1 = np.array([])
arr2 = np.array([1, 2, 3])

if arr1.size == 0 and arr2.size == 0:
    # Handle empty arrays
else:
    np.concatenate((arr1, arr2))

Solution 2: Check arrays are defined or not

Before concatenating the arrays always check whether the array you want to concatenate is defined or not. If all the arrays are defined then concatenate otherwise not.

Solution 3:Check the dimensions

Always check the dimensions of the arrays you want to concatenate. If the size or shape of any one array is different than the other then don’t concatenate.

Conclusion

Valueerror: Need at Least One array to Concatenate when you try to concatenate arrays and one of both arrays is empty. To solve this error always check the emptiness of the array before concatenating. The above are the causes and solutions for this value error.

That’s all for now. I hope you have liked this tutorial. If you have any queries then you can contact us for more help.

Join our list

Subscribe to our mailing list and get interesting stuff and updates to your email inbox.

We respect your privacy and take protecting it seriously

Thank you for signup. A Confirmation Email has been sent to your Email Address.

Something went wrong.