In [1]: import pandas as pd
In [2]: df = pd.DataFrame(columns = ['A', 'B', 'C'])
In [3]: df
Out[3]: 
Empty DataFrame
Columns: [A, B, C]
Index: []
Appending a row by a single column value:
In [4]: df.loc[0, 'A'] = 1
In [5]: df
Out[5]: 
   A    B    C
0  1  NaN  NaN
Appending a ...