Use iloc to access by position (rather than label):
In [11]: df = pd.DataFrame([[1, 2], [3, 4]], ['a', 'b'], ['A', 'B'])
In [12]: df
Out[12]:
A B
a 1 2
b 3 4
In [13]: df.iloc[0] # first row in a DataFrame
Out[13]:
A 1
B 2
Name: a, dtype: int64
In [14]: df['A'].iloc[0] # first item in a Series (Column)
Out[14]: 1