In this article, we will discuss different ways to select the last N columns of a dataframe in pandas.
Table of Contents
- Use iloc[] to select last N columns of pandas dataframe.
- Use [] to select last N columns of pandas dataframe.
- Use tail() to select last N columns of pandas dataframe.
There are different ways to select the last N columns of a dataframe. Let’s discuss them one by one,
Use iloc[] to select last N columns of pandas dataframe
In Pandas, the Dataframe provides an attribute iloc[], to select a portion of the dataframe using position based indexing. This selected portion can be few columns or rows . We can use this attribute to select last N columns of the dataframe. For example,
N = 3 # Select last N columns of dataframe last_n_column = df.iloc[: , -N:]
We selected a portion of dataframe object, that included all rows, but only last N columns of the dataframe.
How did it work?
The syntax of dataframe.iloc[] is like,
df.iloc[row_start:row_end , col_start, col_end]
Arguments:
- row_start: The row index/position from where it should start selection. Default is 0.
- row_end: The row index/position from where it should end the selection i.e. select till row_end-1. Default is till the last row of the dataframe.
- col_start: The column index/position from where it should start selection. Default is 0.
- col_end: The column index/position from where it should end the selection i.e. select till end-1. Default is till the last column of the dataframe.
It returns a portion of the dataframe that includes rows from row_start to row_end-1 and columns from col_start to col_end-1.
To select the last N columns of the dataframe use negative index and and select from column index -N till end i.e (-N:) and select all rows using default values (:),
N = 3 # Select last 3 columns of dataframe last_n_column = df.iloc[: , -N:]
We provided the range to select the columns from -N position till the last column, to select the last N columns, therefore it returned a dataframe. Checkout complete example to select last N columns of dataframe using iloc,
import pandas as pd
# List of Tuples
empoyees = [('Jack', 34, 11, 51, 33, 34, 77, 88) ,
('Riti', 31, 12, 71, 56, 55, 99, 11) ,
('Aadi', 16, 13, 11, 44, 55, 33, 54) ,
('Mark', 41, 14, 12, 78, 89, 46, 56)]
# Create a DataFrame object
df = pd.DataFrame( empoyees)
print("Contents of the Dataframe : ")
print(df)
N = 3
# Select last 3 columns of dataframe
last_n_column = df.iloc[: , -N:]
print("Last 3 Columns Of Dataframe : ")
print(last_n_column)
print('Type:')
print(type(last_n_column))
Output:
Contents of the Dataframe :
0 1 2 3 4 5 6 7
0 Jack 34 11 51 33 34 77 88
1 Riti 31 12 71 56 55 99 11
2 Aadi 16 13 11 44 55 33 54
3 Mark 41 14 12 78 89 46 56
Last 3 Columns Of Dataframe :
5 6 7
0 34 77 88
1 55 99 11
2 55 33 54
3 89 46 56
Type:
<class 'pandas.core.frame.DataFrame'>
We selected the last N columns of the dataframe.
Select last N columns of pandas dataframe using []
We can fetch the column names of dataframe as a sequence and then select the last N column names. Then using those column names, we can select the last N columns of dataframe using subscript operator i.e. []. For example,
print("Contents of the Dataframe : ")
print(df)
N = 3
# Select last 3 columns of dataframe
last_n_column = df[df.columns[-N:]]
print("Last 3 Columns Of Dataframe : ")
print(last_n_column)
print('Type:')
print(type(last_n_column))
Output:
Contents of the Dataframe :
0 1 2 3 4 5 6 7
0 Jack 34 11 51 33 34 77 88
1 Riti 31 12 71 56 55 99 11
2 Aadi 16 13 11 44 55 33 54
3 Mark 41 14 12 78 89 46 56
Last 3 Columns Of Dataframe :
5 6 7
0 34 77 88
1 55 99 11
2 55 33 54
3 89 46 56
Type:
<class 'pandas.core.frame.DataFrame'>
Use tail() to select the last N columns of pandas dataframe
We can use the dataframe.T attribute to get a transposed view of the dataframe and then call the tail(N) function on that view to select the last N rows i.e. the last N columns of the original dataframe. Then transpose back that dataframe object to have the column contents as a dataframe object. For example,
print("Contents of the Dataframe : ")
print(df)
N = 3
# Select last 3 columns
last_n_column = df.T.tail(3).T
print("Last 3 Columns Of Dataframe : ")
print(last_n_column)
print('Type:')
print(type(last_n_column))
Output:
Contents of the Dataframe :
0 1 2 3 4 5 6 7
0 Jack 34 11 51 33 34 77 88
1 Riti 31 12 71 56 55 99 11
2 Aadi 16 13 11 44 55 33 54
3 Mark 41 14 12 78 89 46 56
Last 3 Columns Of Dataframe :
5 6 7
0 34 77 88
1 55 99 11
2 55 33 54
3 89 46 56
Type:
<class 'pandas.core.frame.DataFrame'>
It returned the last N columns of dataframe as a dataframe object.
Summary
We learned different ways to get the last N columns of a dataframe in pandas.