pandas filter

Conditions filter

• Be filtered through a row loc, can also be assigned to the line after the filter

import pandas as pd

df = pd.DataFrame({"name": ["yang", "wang", "li", "zhang", "zhao"], "score": [100, 78, 112, 61, 94],
                   "age": [16, 18, 16, 17, 17]})

• • Get name for the yang of the score values:

>>> df.loc[df["name"] == "yang", 'score']

0 100
Name: sorce, dtype: object

• • query method to filter query

df.query("name=='yang'")
   name sorce
0  yang   100

Multi-condition filter

• Score greater than 90, the age is 17 rows

>>> df[(df.score > 90) & (df.age == 17)]
   name  score  age
4  zhao     94   17
>>> 
>>> df.loc[(df.score > 90) & (df.age == 17)]
   name  score  age
4  zhao     94   17

# 注意在逻辑操作符两边的过滤条件必须使用小括号括起来，否则条件过滤不起作用
# 过滤后赋值

>>> mask = (df.score > 90) & (df.age == 17)

mask
0 False
1 False
2 False
3 False
4 True
dtype: bool 

 >>> df.loc[mask, 'score'] = df.loc[mask, 'score'] + 1