人工智障学习记录 
import pandas as pd
import numpy as np
df = pd.DataFrame({
'姓名':['张三','李四','王五','赵六'],
'年龄':[18,19,20,21],
'性别':['男','男','女','女'],
'数学':[90,85,88,92],
'英语':[80,75,78,85]
})
# print(df['姓名'])
# print(df[df['数学']>85])
# print(df.loc[2])
# print(df.iloc[2])
# print(df.iloc[3,4])
# print(df[df['性别'] == '女']['英语'])
# print(df[(df['年龄']>17) & (df['年龄']<=20)])
# print(df[df['数学']+df['英语']>170])
# print(df.iloc[1:2,4:5])
# print(df[(df['性别'] == '男')&(df['数学']>85)])
# df.loc[df['姓名'] == '张三','英语'] = 90
# df.loc[df['姓名'] == '王五','性别'] = '保密'
# df.loc[df['英语'] < 80,'英语'] += 5
# print(df.rename(columns={'数学':'aaaa'}))
# df.loc[df['姓名'] == '赵六','年龄'] = 22
# df.loc[df['年龄']>19,'年龄']='成年人'
#找到李四 把李四的成绩乘以1.2,只保留整数..不会！！！
06-24-凌晨