How to merge two rows in a dataframe pandas

You could use max with transpose like

In [2103]: df.max().to_frame().T
Out[2103]:
      PC Rating CY Rating PY  HT MV1 MV2
0  DE101       AA+        AA  GV  10  20

You can make use of DF.combine_first() method after separating the DF into 2 parts where the null values in the first half would be replaced with the finite values in the other half while keeping it's other finite values untouched:

df.head(1).combine_first(df.tail(1))
# Practically this is same as → df.head(1).fillna(df.tail(1))

---

Incase there are columns of mixed datatype, partitioning them into it's constituent dtype columns and then performing various operations on it would be feasible by chaining them across.

obj_df = df.select_dtypes(include=[np.object])
num_df = df.select_dtypes(exclude=[np.object])

obj_df.head(1).combine_first(obj_df.tail(1)).join(num_df.head(1).add(num_df.tail(1)))