dataframe 选取某几列

import pandas as pd
df = pd.DataFrame({‘a’:[3,2,4,5,6],’b’:range(5,10)})
df[[‘a’]]

取df的feature和label

df[df.columns[:-1]]

注意取一列默认为series

df[df.columns[-1]]

group by

df_user.sexes.value_counts()

dataframe to excel

df_user.to_excel(‘user.xls’,columns=[‘names’,’sexes’,’cities’,’signatures’,’remark_names’], index=False)
df_user = pd.DataFrame.from_dict(user_data)