Python3.x 找到在指定列的另一个分组中存在重复的行.

对于数据集df，我想按列B中foo和bar的两组进行分组，并标识这两组中存在的重复行.我怎样才能做到这一点呢？

df = pd.DataFrame({'A': [1, 2, 2, 3, 3, 1],
                   'B': ['foo', 'bar', 'foo', 'bar', 'foo', 'foo']})
df = df.sort_values('B')
df
Out[15]: 
   A    B
1  2  bar
3  3  bar
0  1  foo
2  2  foo
4  3  foo
5  1  foo

预期结果:

   A    B  Indicator
1  2  bar  True  # value 2 also present in foo, so returns True
3  3  bar  True  # value 3 also present in foo, so returns True
0  1  foo  False  # value 1 only present in foo, so returns False
2  2  foo  True  # value 2 also present in bar, so returns True
4  3  foo  True  # value 3 also present in bar, so returns True
5  1  foo  False  # value 1 only present in foo, so returns False

Updates:个

假设列B具有more than 2 categories，则样本数据df如下:

df = pd.DataFrame({'A': [1, 2, 2, 3, 3, 2, 1],  'B': ['foo', 'bar', 'foo', 'bar', 'foo', 'baz', 'baz']})
df = df.sort_values('B')
df
Out[30]: 
   A    B
1  2  bar
3  3  bar
5  2  baz
6  1  baz
0  1  foo
2  2  foo
4  3  foo

在这种情况下，预期结果如下所示:

   A    B  Indicator
1  2  bar  True  # The value 2 occurs in categories baz, bar, and foo, so returns True.
3  3  bar  False  # The value 3 only occurs in categories bar and foo, so returns False.
5  2  baz  True  # The value 2 occurs in categories baz, bar, and foo, so returns True.
6  1  baz  False  # The value 1 only occurs in categories baz and foo, so returns False.
0  1  foo  False  # The value 1 only occurs in categories baz and foo, so returns False.
2  2  foo  True  # The value 2 occurs in categories baz, bar, and foo, so returns True.
4  3  foo  False  # The value 3 only occurs in categories bar and foo, so returns False.