How can I extract the nth row of a pandas data frame as a pandas data frame?

Question

Suppose a Pandas data frame looks like:

X_test.head(4)
    BoxRatio  Thrust  Velocity  OnBalRun  vwapGain
5     -0.163  -0.817     0.741     1.702     0.218
8      0.000   0.000     0.732     1.798     0.307
11     0.417  -0.298     2.036     4.107     1.793
13     0.054  -0.574     1.323     2.553     1.185

How can I extract the third row (as row3) as a pd data frame? In other words, row3.shape should be (1,5) and row3.head() should be:

 0.417  -0.298     2.036     4.107     1.793

Answer 1

Use .iloc with double brackets to extract a DataFrame, or single brackets to pull out a Series.

>>> import pandas as pd
>>> df = pd.DataFrame({'col1': [1, 2], 'col2': [3, 4]})
>>> df
   col1  col2
0     1     3
1     2     4
>>> df.iloc[[1]]  # DataFrame result
   col1  col2
1     2     4
>>> df.iloc[1]  # Series result
col1    2
col2    4
Name: 1, dtype: int64

This extends to other forms of DataFrame indexing as well, namely .loc and .__getitem__() :

>>> df.loc[:, ['col2']]
   col2
0     3
1     4

>>> df[['col2']]
   col2
0     3
1     4

Answer 2

Alternatively you can also use take :

In [4]: df.take([2])
Out[4]: 
    BoxRatio  Thrust  Velocity  OnBalRun  vwapGain
11     0.417  -0.298     2.036     4.107     1.793