限制class的属性，只允许添加被许可的属性 （slots）
python class (5): 使用装饰器@property来设定属性
python的装饰器(decorator) @property
python class (6): python 2 and python 3 class definition with super()
a short notes from stackoverflow about super() in python2 and python3
python regular expression
python regular expression in text processing
working with text data in sklearn
text analysis to count word frequency, training data and using pipeline to automatic the job
first row partition by var order by the numeric var
SQL: get first row partition by variable B order by the valeue of variable C
best subset regression in python
numpy introduction 01
pandas data describe to get summary information
python recursion function
recursion function is very useful in math/stat like decision tree or optimization. this is an example on how to build recursion function