Pandas：使用波浪号运算符返回带有两个过滤器的逆向数据
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Pandas: Using the tilde operator to return inverse data with two filters
提问by RDJ
I'm filtering on two DataFrame columns using isin. Aim is to return two distinct DataFrames: One where the filter conditions are met and one where they're not. The DataFrames should be exact opposites, in effect. However I can't seem to use the tilde operator in the way I assumed I could.
我正在使用isin. 目标是返回两个不同的 DataFrame：一个满足过滤条件，另一个不满足。实际上，数据帧应该是完全相反的。但是，我似乎无法以我认为可以的方式使用波浪号运算符。
A reproducible example:
一个可重现的例子：
raw_data = {
'id': ['s1', 's2', 's1', 's4', 's2', 's5', 's4', 's2'],
'car': ['ford', 'bmw', 'ford', 'mazda', 'ford', 'bmw', 'audi', 'bmw']}
df_a = pd.DataFrame(raw_data, columns= ['id', 'car'])
values1 = ['s1', 's2']
values2 = ['bmw', 'ford']
df_a[(df_a['id'].isin(values1)) & (df_a['car'].isin(values2))]
Returns this:
返回这个：
id car
0 s1 ford
1 s2 bmw
2 s1 ford
4 s2 ford
7 s2 bmw
Which is correct. But if try to reverse that using:
哪个是正确的。但是，如果尝试使用以下方法扭转该情况：
df_a[~(df_a['id'].isin(values1)) & (df_a['car'].isin(values2))]
df_a[~(df_a['id'].isin(values1)) & (df_a['car'].isin(values2))]
I get:
我得到：
id car
5 s5 bmw
Which is not the inverse. I've tried adding a second tilde to the second filter but can't make it work. Where am I going wrong, or is there a better way to do this?
这不是相反的。我试过在第二个过滤器中添加第二个波浪号，但无法使其工作。我哪里出错了，还是有更好的方法来做到这一点？
回答by EdChum
You need additional parentheses:
您需要额外的括号：
In [411]:
df_a[~((df_a['id'].isin(values1)) & (df_a['car'].isin(values2)))]
# ^ ^
Out[411]:
id car
3 s4 mazda
5 s5 bmw
6 s4 audi
What you did was invert only the first condition.
你所做的只是反转第一个条件。
