[英]Selecting rows based on multiple columns in pandas - why are these two commands different?
我有一個 pandas DataFrame:
import pandas as pd
a = [0,0,1,1,2,7]
b = [1,0,0,1,1,4]
df = pd.DataFrame(list(zip(a,b)), columns = ('a','b'))
df
a b
0 0 1
1 0 0
2 1 0
3 1 1
4 2 1
5 7 4
我想 select a和b都大於零的所有行:
為什么這個命令只返回一些需要的行:
df[(df['a'] & df['b'])>0]
a b
3 1 1
5 7 4
雖然此其他命令返回所有所需的行:
df[((df['a']>0) & (df['b']>0))]
a b
3 1 1
4 2 1
5 7 4
這意味着總和應該大於1? 這些列中是否也有負值?
df[df.sum(axis=1)>1]
a b
3 1 1
4 2 1
5 7 4
或者
rows where values is greater than zero are summed along rows
df[df[df>0].sum(axis=1)>1]
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