python - Pandas Dataframe Find Rows Where all Columns Equal

Question

I have a dataframe that has characters in it - I want a boolean result by row that tells me if all columns for that row have the same value.

For example, I have

df = [  a   b   c   d

0  'C'   'C'   'C'   'C' 

1  'C'   'C'   'A'   'A'

2  'A'   'A'   'A'   'A' ]

and I want the result to be

0  True

1  False

2  True

I've tried .all but it seems I can only check if all are equal to one letter. The only other way I can think of doing it is by doing a unique on each row and see if that equals 1? Thanks in advance.

Answer 1

I think the cleanest way is to check all columns against the first column using eq:

In [11]: df
Out[11]: 
   a  b  c  d
0  C  C  C  C
1  C  C  A  A
2  A  A  A  A

In [12]: df.iloc[:, 0]
Out[12]: 
0    C
1    C
2    A
Name: a, dtype: object

In [13]: df.eq(df.iloc[:, 0], axis=0)
Out[13]: 
      a     b      c      d
0  True  True   True   True
1  True  True  False  False
2  True  True   True   True

Now you can use all (if they are all equal to the first item, they are all equal):

In [14]: df.eq(df.iloc[:, 0], axis=0).all(1)
Out[14]: 
0     True
1    False
2     True
dtype: bool