import pandas as pd
columns = ["A", "B", "C"]
data = [[1, 11, 111],
        [2, 22, 222],
        [3, 33, 333]]
df = pd.DataFrame(data=data, columns=columns)
df

Out[1]:
    A   B   C
0   1   11  111
1   2   22  222
2   3   33  333


mdict = {}
for c in df.columns:
    mdict.update(dict(zip(df[c], df['A'])))
mdict

Out[2]:
{1: 1, 2: 2, 3: 3, 11: 1, 22: 2, 33: 3, 111: 1, 222: 2, 333: 3}

df2 = pd.DataFrame(data=[1, 11, 111, 2, 22, 222, 3, 33, 333], columns=['D'])
df2['D'] = df2['D'].map(mdict)
df2

Out[3]:
    D
0   1
1   1
2   1
3   2
4   2
5   2
6   3
7   3
8   3