pandas 熊猫左连接，其中多列上的右为空

pandas left join where right is null on multiple columns

提问by edoedoedo

I have two pandas df x and y, both with the same 3 columns A B C (not nullable). I need to create a new df z, obtained by "subtracting from x the rows which are entirely identical to the rows of y", i.e. a

我有两只Pandas df x 和 y，它们都具有相同的 3 列 ABC（不可为空）。我需要创建一个新的 df z，通过“从 x 中减去与 y 的行完全相同的行”获得，即

x left join y on x.A=y.A and x.B=y.B and x.C=y.C
where y.A is null

How would I do that? Got stuck with indexes, concat, merge, join, ...

我该怎么做？被索引、连接、合并、连接、......

Example:

例子：

dataframe x
A    B    C
q1   q2   q3
q4   q2   q3
q7   q2   q9

dataframe y
A    B    C
q4   q2   q3

dataframe z
A    B    C
q1   q2   q3
q7   q2   q9

回答by jezrael

I think need mergewith indicator and filter only rows from leftDataFrame:

我认为需要merge使用指标并仅从以下位置过滤行leftDataFrame：

df = x.merge(y, indicator='i', how='outer').query('i == "left_only"').drop('i', 1)
print (df)
    A   B    C
0  q1  q2   q3
2  q7  q2  q93