pandas_dataframe_and_rows

import pandas as pd

df = pd.DataFrame(
        {"a" : [4 ,5, 6],
        "b" : [7, 8, 9],
        "c" : [10, 11, 12]},
        index = [1, 2, 3])

df
a b c
1 4 7 10
2 5 8 11
3 6 9 12 
df.loc[3, "a"]

6

df.loc[[1, 2], ["a", "b"]]
a b
1 4 7
2 5 8 
df = pd.DataFrame(
        [[4, 7, 10],
        [5, 8, 11],
        [6, 9, 12]],
        index=[1, 2, 3],
        columns=["a", 'b', 'c'])
df
a b c
1 4 7 10
2 5 8 11
3 6 9 12 
import numpy as np
df = pd.DataFrame(
        {"a" : [4 ,5, 6, 6, np.nan],
        "b" : [7, 8, np.nan, 9, 9],
        "c" : [10, 11, 12, np.nan, 12]},
        index = pd.MultiIndex.from_tuples(
        [('d',1),('d',2),('e',2),('e',3),('e',4)],
        names=['n','v']))
df
a b c
n v
d 1 4.0 7.0 10.0
2 5.0 8.0 11.0
e 2 6.0 NaN 12.0
3 6.0 9.0 NaN
4 NaN 9.0 12.0