pandas.get_dummies(data, prefix=None, prefix_sep='_', dummy_na=False, columns=None,sparse=False, drop_first=False, dtype=None) -> 'DataFrame'
Convert categorical variable into dummy/indicator variables.
It’s a function which can turn a categprical variable into a series of zeros and ones, which makes them a lot easier to quantify and compare.
不管是输入的是Series还是DataFrame，get_dummies()提取两个关键概念,return 一个DataFrame。
返回的DataFrame，columns是所有元素的枚举，index是源数据的记录条目数。如果源数据中为NaN，则新增一条记录，全0。
