The default of the `iid` parameter will change from True to False in version 0.22 and will be removed in 0.24

from sklearn.model_selection import GridSearchCV
from sklearn.model_selection import train_test_split

Anaconda 3 libsite-packagessklearnmodel_selection\_search.py:814:
DeprecationWarning: The default of the `iid` parameter will change from True to False in version 0.22 and will be removed in 0.24.
This will change numeric results when test-set sizes are unequal.  

 https://machinelearningmastery.com/how-to-fix-futurewarning-messages-in-scikit-learn/