ValueError: With n_samples=1, test_size=0.2 and train_size=None, the resulting train set will be

ValueError: With n_samples=1, test_size=0.2 and train_size=None, the resulting train set will be empty.

这个问题是scikit-learn版本较高时出现的问题，sklearn have problems with the version 0.20.0+ of scikt-learn，可以查看下 sklearn的版本

python
>>import sklearn
>>sklearn.__version__

version前后都是两个下划线

可以改为安装较低版本：

Windows: pip uninstall scikit-learn 
Linux: sudo python36 -m pip uninstall scikit-learn

and install:

Windows: pip install scikit-learn==0.19.1 
Linux: sudo python36 -m pip install scikit-learn==0.19.1