Python 如何在熊猫数据框列中选择一系列值？
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How to select a range of values in a pandas dataframe column?
提问by ShanZhengYang
import pandas as pd
import numpy as np
data = 'filename.csv'
df = pd.DataFrame(data)
df
one two three four five
a 0.469112 -0.282863 -1.509059 bar True
b 0.932424 1.224234 7.823421 bar False
c -1.135632 1.212112 -0.173215 bar False
d 0.232424 2.342112 0.982342 unbar True
e 0.119209 -1.044236 -0.861849 bar True
f -2.104569 -0.494929 1.071804 bar False
I would like to select a range for a certain column, let's say column two. I would like to select all values between -0.5 and +0.5. How does one do this?
我想为某个列选择一个范围，比如说 column two。我想选择 -0.5 和 +0.5 之间的所有值。如何做到这一点？
I expected to use
我希望使用
-0.5 < df["two"] < 0.5
But this (naturally) gives a ValueError:
但这（自然地）给出了一个 ValueError：
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
I tried
我试过
-0.5 (< df["two"] < 0.5)
But this outputs all True.
但这输出所有True.
The correct output should be
正确的输出应该是
0 True
1 False
2 False
3 False
4 False
5 True
What is the correct way to find a range of values in a pandas dataframe column?
在 Pandas 数据框列中查找一系列值的正确方法是什么？
EDIT: Question
编辑：问题
Using .between()with
使用.between()与
df['two'].between(-0.5, 0.5, inclusive=False)
would would be the difference between
将是之间的区别
-0.5 < df['two'] < 0.5
and inequalities like
和不平等，如
-0.5 =< df['two'] < 0.5
?
?
回答by root
Use betweenwith inclusive=Falsefor strict inequalities:
使用between有inclusive=False严格的不平等：
df['two'].between(-0.5, 0.5, inclusive=False)
The inclusiveparameter determines if the endpoints are included or not (True: <=, False: <). This applies to both signs. If you want mixed inequalities, you'll need to code them explicitly:
该inclusive参数确定是否包含端点（True: <=, False: <）。这适用于两个标志。如果你想要混合不等式，你需要明确地对它们进行编码：
(df['two'] >= -0.5) & (df['two'] < 0.5)
回答by Kartik
.betweenis a good solution, but if you want finer control use this:
.between是一个很好的解决方案，但如果你想要更好的控制使用这个：
(0.5 <= df['two']) & (df['two'] < 0.5)
The operator &is different from and. The other operators are |for or, ~for not. See this discussionfor more info.
运算符&不同于and. 其他运算符是|for or，~for not。有关更多信息，请参阅此讨论。
Your statement was the same as this:
你的陈述是这样的：
(0.5 <= df['two']) and (df['two'] < 0.5)
Hence it raised the error.
因此它引发了错误。
