Python 基于另一列熊猫数据框提取列值
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extract column value based on another column pandas dataframe
提问by Anderson Zhu
I am kind of getting stuck on extracting value of one variable conditioning on another variable. For example, the following dataframe:
我有点卡在提取一个变量条件下另一个变量的值上。例如，以下数据框：
A B
p1 1
p1 2
p3 3
p2 4
How can I get the value of Awhen B=3? Every time when I extracted the value of A, I got an object, not a string.
我怎样才能获得Awhen的价值B=3？每次提取 的值时A，都会得到一个对象，而不是字符串。
回答by Anton Protopopov
You could use locto get series which satisfying your condition and then ilocto get first element:
您可以使用loc获取满足您条件的系列，然后iloc获取第一个元素：
In [2]: df
Out[2]:
A B
0 p1 1
1 p1 2
2 p3 3
3 p2 4
In [3]: df.loc[df['B'] == 3, 'A']
Out[3]:
2 p3
Name: A, dtype: object
In [4]: df.loc[df['B'] == 3, 'A'].iloc[0]
Out[4]: 'p3'
回答by PhilChang
You can try query, which is less typing:
你可以试试query，这是少打字：
df.query('B==3')['A']
回答by emited
df[df['B']==3]['A'], assuming df is your pandas.DataFrame.
df[df['B']==3]['A']，假设 df 是你的 pandas.DataFrame。
回答by Baz
Use df[df['B']==3]['A'].valuesif you just want item itself without the brackets
df[df['B']==3]['A'].values如果您只想要没有括号的项目本身，请使用
回答by Dheeraj Pranav
male_avgtip=(tips_data.loc[tips_data['sex'] == 'Male', 'tip']).mean()
I have also worked on this clausing and extraction operations for my assignment.
我还为我的作业研究了这个从句和提取操作。
