when combining different dataframes how to get same columns to merge code example

Example 1: merge two columns pandas

df["period"] = df["Year"] + df["quarter"]

Example 2: concact geodataframe python

>>> s1 = pd.Series(['a', 'b'])
>>> s2 = pd.Series(['c', 'd'])
>>> pd.concat([s1, s2])
0    a
1    b
0    c
1    d
dtype: object