python push to dataframe pandas

df = df.append({'a':1, 'b':2}, ignore_index=True)

df = pd.DataFrame({
    'a':[1,2,3],
    'b':[5,6,7]
})

df2 = pd.DataFrame({
    'a':[11,12,13],
    'b':[15,16,17]
})

df = df.append(df2, ignore_index = True )

print(df)

>>> df = pd.DataFrame([[1, 2], [3, 4]], columns=list('AB'))
>>> df
   A  B
0  1  2
1  3  4
>>> df2 = pd.DataFrame([[5, 6], [7, 8]], columns=list('AB'))
>>> df.append(df2)
   A  B
0  1  2
1  3  4
0  5  6
1  7  8