One error you may encounter when using Python is:
ModuleNotFoundError: No module named 'sklearn.cross_validation'
This error usually occurs when you attempt to import the train_test_split function from sklearn using the following line:
from sklearn.cross_validation import train_test_split
However, the cross_validation sub-module has been replaced with the model_selection sub-module, so you need to use the following line instead:
from sklearn.model_selection import train_test_split
The following example shows how to resolve this error in practice.
How to Reproduce the Error
Suppose we would like to use the train_test_split function from sklearn to split a pandas DataFrame into training and testing sets.
Suppose we attempt to use the following code to import the train_test_split function:
from sklearn.cross_validation import train_test_split ModuleNotFoundError: No module named 'sklearn.cross_validation'
We receive an error because we used the wrong sub-module name when attempting to import the train_test_split function.
How to Fix the Error
To fix this error, we simply need to use the model_selection sub-module instead:
from sklearn.model_selection import train_test_split
This time we don’t receive any error.
We could then proceed to use the train_test_split function to split a pandas DataFrame into a training and testing set:
from sklearn.model_selection import train_test_split import pandas as pd import numpy as np #make this example reproducible np.random.seed(1) #create DataFrame with 1000 rows and 3 columns df = pd.DataFrame({'x1': np.random.randint(30, size=1000), 'x2': np.random.randint(12, size=1000), 'y': np.random.randint(2, size=1000)}) #split original DataFrame into training and testing sets train, test = train_test_split(df, test_size=0.2, random_state=0) #view first few rows of each set print(train.head()) x1 x2 y 687 16 2 0 500 18 2 1 332 4 10 1 979 2 8 1 817 11 1 0 print(test.head()) x1 x2 y 993 22 1 1 859 27 6 0 298 27 8 1 553 20 6 0 672 9 2 1
We’re successfully able to use the train_test_split function without any error.
Additional Resources
The following tutorials explain how to fix other common errors in Python:
How to Fix: columns overlap but no suffix specified
How to Fix: ‘numpy.ndarray’ object has no attribute ‘append’
How to Fix: if using all scalar values, you must pass an index
How to Fix: ValueError: cannot convert float NaN to integer