根据大 pandas 列中的值从DataFrame中选择行 [英] Select rows from a DataFrame based on values in a column in pandas
问题描述
如何根据大熊猫某栏中的值从DataFrame中选择行?
在SQL中,我将使用:
select * from table where colume_name = some_value。
我试图看熊猫文档,但没有立即找到答案。 >
要选择列值等于标量的行, some_value
,使用 ==
:
df.loc [df ['column_name '] == some_value]
要选择列值为可迭代的行, some_values
,使用 isin
:
df.loc [df ['column_name']。isin(some_values)]
将多个条件与&
:
df.loc [(df ['column_name' ] == some_value)& df ['other_column']。isin(some_values)]
要选择列值不等于 some_value
的行,请使用!=
:
df.loc [df ['column_name']!= some_value]
/ pre>
isin
返回一个布尔系列,因此要选择其值为的行不是在some_values
中,使用〜
取消布尔系列:df.loc [〜df ['column_name']。isin(some_values)]
例如,
将大熊猫导入为pd
import numpy as np
df = pd.DataFrame({'A':'foo bar foo bar foo bar foo foo'.split(),
'B':'one one two three两个一个三'.split(),
'C':np.arange(8),'D':np.arange(8)* 2})
print(df)
#ABCD
#0 foo one 0 0
#1 ba r one 1 2
#2 foo two 2 4
#3 bar three 3 6
#4 foo two 4 8
#5 bar two 5 10
#6 foo one 6 12
#7 foo three 7 14
print(df.loc [df ['A'] =='foo'])
ABCD
0 foo one 0 0
2 foo two 2 4
4 foo two 4 8
6 foo one 6 12
7 foo three 7 14
如果您要包含多个值,请将它们放在
列表中(或更一般地,任何可迭代的),并使用isin
:print (df.loc [df ['B']。isin(['one','three'])])
ABCD
0 foo one 0 0
1 bar one 1 2
3 bar三3 6
6 foo one 6 12
7 foo three 7 14
请注意,如何永远,如果你想这么做很多次,那么
首先创建一个索引,然后使用df.loc
来更有效:df = df.set_index(['B'])
print(df.loc ['one'])
产生
ACD
B
一个foo 0 0
一个酒吧1 2
一个foo 6 12
或者,要包含索引中的多个值,请使用
df.index.isin
:df.loc [df.index.isin(['one','two'])]
ACD
B
一个foo 0 0
一个酒吧1 2
两个foo 2 4
两个foo 4 8
两个酒吧5 10
一个foo 6 12
How to select rows from a DataFrame based on values in some column in pandas?
In SQL I would use:select * from table where colume_name = some_value.
I tried to look at pandas documentation but did not immediately find the answer.
解决方案To select rows whose column value equals a scalar,
some_value
, use==
:df.loc[df['column_name'] == some_value]
To select rows whose column value is in an iterable,
some_values
, useisin
:df.loc[df['column_name'].isin(some_values)]
Combine multiple conditions with
&
:df.loc[(df['column_name'] == some_value) & df['other_column'].isin(some_values)]
To select rows whose column value does not equal
some_value
, use!=
:df.loc[df['column_name'] != some_value]
isin
returns a boolean Series, so to select rows whose value is not insome_values
, negate the boolean Series using~
:df.loc[~df['column_name'].isin(some_values)]
For example,
import pandas as pd import numpy as np df = pd.DataFrame({'A': 'foo bar foo bar foo bar foo foo'.split(), 'B': 'one one two three two two one three'.split(), 'C': np.arange(8), 'D': np.arange(8) * 2}) print(df) # A B C D # 0 foo one 0 0 # 1 bar one 1 2 # 2 foo two 2 4 # 3 bar three 3 6 # 4 foo two 4 8 # 5 bar two 5 10 # 6 foo one 6 12 # 7 foo three 7 14 print(df.loc[df['A'] == 'foo'])
yields
A B C D 0 foo one 0 0 2 foo two 2 4 4 foo two 4 8 6 foo one 6 12 7 foo three 7 14
If you have multiple values you want to include, put them in a list (or more generally, any iterable) and use
isin
:print(df.loc[df['B'].isin(['one','three'])])
yields
A B C D 0 foo one 0 0 1 bar one 1 2 3 bar three 3 6 6 foo one 6 12 7 foo three 7 14
Note, however, that if you wish to do this many times, it is more efficient to make an index first, and then use
df.loc
:df = df.set_index(['B']) print(df.loc['one'])
yields
A C D B one foo 0 0 one bar 1 2 one foo 6 12
or, to include multiple values from the index use
df.index.isin
:df.loc[df.index.isin(['one','two'])]
yields
A C D B one foo 0 0 one bar 1 2 two foo 2 4 two foo 4 8 two bar 5 10 one foo 6 12
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