NumPy RuntimeWarning: Mean of empty slice in Python
Here, we will see how to fix “Numpy Runtimewarning: Mean Of Empty Slice” in Python. In this article, we will see the reasons for it’s occurrence and also the solution of NumPy RuntimeWarning: Mean of empty slice in Python.
What is NumPy RuntimeWarning: Mean of empty slice in Python?
The NumPy RuntimeWarning: Mean of empty slice in Python occurs when attempting to calculate the mean of an empty NumPy array slice. This warning is an indication that the code is trying to perform a mathematical operation on a subset of an array that has no elements. Understanding the reasons behind this warning is crucial for resolving the issue effectively.
Syntax:
Numpy Runtimewarning: Mean Of Empty Slice
Below is the reason why NumPy RuntimeWarning: Mean of empty slice occurs in Python:
- Empty Slicing
- Invalid Indexing
Empty Array
In this example, the code creates an empty NumPy array, and then attempts to calculate the mean of a slice with no elements, triggering a “RuntimeWarning: Mean Of Empty Slice” because there are no values to compute the mean from.
Python3
import numpy as np #defining the array empty_array = np.array([]) np.mean(empty_array) |
Output
/usr/local/lib/python3.7/site-packages/numpy/core/fromnumeric.py:3441: RuntimeWarning: Mean of empty slice.
out=out, **kwargs)
/usr/local/lib/python3.7/site-packages/numpy/core/_methods.py:189: RuntimeWarning: invalid value encountered in double_scalars
ret = ret.dtype.type(ret / rcount)
Invalid Indexing
In this example, below code creates an empty slice with indices [5:2] from a NumPy array, and then attempts to calculate the mean of this empty slice, resulting in a “RuntimeWarning: Mean Of Empty Slice” since there are no elements in the slice.
Python3
import numpy as np data = np.array([ 1 , 2 , 3 , 4 , 5 ]) empty_slice = data[ 5 : 2 ] output = np.mean(empty_slice) print (output) |
Output
packages/numpy/core/fromnumeric.py:3504: RuntimeWarning: Mean of empty slice.
return _methods._mean(a, axis=axis, dtype=dtype,
/usr/local/lib/python3.10/dist-packages/numpy/core/_methods.py:129: RuntimeWarning: invalid value encountered in scalar divide
ret = ret.dtype.type(ret / rcount)
Solution for NumPy RuntimeWarning: Mean of empty slice in Python
Below, are the approaches to solve NumPy RuntimeWarning: Mean of empty slice in Python:
- Check for empty arrays
- Correcting indexing
Check For Empty array
In this example, below code creates an empty NumPy array, checks if it’s non-empty before calculating the mean of a slice, and prints the mean if there are elements, or a message stating that the array is empty if it is indeed empty.
Python3
import numpy as np empty_array = np.array([]) # Checking for empty array before calculating the mean if len (empty_array) > 0 : mean_value = np.mean(empty_array[ 1 : 3 ]) print ( "Mean:" , mean_value) else : print ( "Array is empty." ) |
Array is empty.
Correct Indexing
In this example, below code creates a NumPy array with a single element and correctly calculates the mean of the array using appropriate indexing to avoid accessing elements beyond the array bounds.
Python3
import numpy as np single_element_array = np.array([ 42 ]) # Correcting indexing to prevent accessing elements beyond array bounds mean_value = np.mean(single_element_array[: 1 ]) print ( "Mean:" , mean_value) |
Mean: 42.0
Contact Us