How to delete first N columns of pandas dataframe

In this article, we will discuss different ways to delete first N columns of a dataframe in python.

Use iloc to drop first 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 a few columns or rows . We can use this attribute to select all the columns except first N columns of the dataframe and then assign back that to the original variable. It will give an effect that we have deleted the first N columns from the dataframe. For example,

N = 3
# Drop first N columns of dataframe
df = df.iloc[: , N:]

We selected a portion of dataframe, that included all rows, but it selected only last (size – N) columns. Then assigned this back to the same variable. So, basically it removed the first N columns of dataframe.

How did it work?

The syntax of dataframe.iloc[] is like,

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df.iloc[row_start:row_end , col_start, col_end]
  • 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 col_end-1. Default is till the last column of the dataframe.

It returns a portion of dataframe that includes rows from row_start to row_end-1 and columns from col_start to col_end-1.

To delete the first N columns of the dataframe, just select the columns from column number N till the end and select all rows. As indexing starts from 0, so to select all columns after the N, use –> (N:) i.e. from Nth column till the end. To select all the rows use default values i.e. (:) i.e.

df = df.iloc[: , N:]

Checkout complete example to delete the first 3 columns of dataframe,

import pandas as pd

# List of Tuples
empoyees = [('Jack',    34, 'Sydney',   5) ,
            ('Riti',    31, 'Delhi' ,   7) ,
            ('Aadi',    16, 'London',   11) ,
            ('Mark',    41, 'Delhi' ,   12)]

# Create a DataFrame object
df = pd.DataFrame(  empoyees, 
                    columns=['Name', 'Age', 'City', 'Experience'])

print("Contents of the Dataframe : ")
print(df)

N = 3
# Drop first N columns of dataframe
df = df.iloc[: , N:]

print("Modified Dataframe : ")
print(df)

Output:

Contents of the Dataframe :
   Name  Age    City  Experience
0  Jack   34  Sydney           5
1  Riti   31   Delhi           7
2  Aadi   16  London          11
3  Mark   41   Delhi          12
Modified Dataframe :
   Experience
0           5
1           7
2          11
3          12

Use drop() to remove first N columns of pandas dataframe

In pandas, the dataframe’s drop() function accepts a sequence of column names that it needs to delete from the dataframe. To make sure that it removes the columns only, use argument axis=1 and to make changes in place i.e. in calling dataframe object, pass argument inplace=True.

Checkout complete example to delete the first 3 columns of dataframe,

import pandas as pd

# List of Tuples
empoyees = [('Jack',    34, 'Sydney',   5) ,
            ('Riti',    31, 'Delhi' ,   7) ,
            ('Aadi',    16, 'London',   11) ,
            ('Mark',    41, 'Delhi' ,   12)]


# Create a DataFrame object
df = pd.DataFrame(  empoyees, 
                    columns=['Name', 'Age', 'City', 'Experience'])



print("Contents of the Dataframe : ")
print(df)

N = 3
# Drop first N columns of dataframe
df.drop(columns=df.columns[:N], 
        axis=1, 
        inplace=True)

print("Modified Dataframe : ")
print(df)

Output:

Contents of the Dataframe :
   Name  Age    City  Experience
0  Jack   34  Sydney           5
1  Riti   31   Delhi           7
2  Aadi   16  London          11
3  Mark   41   Delhi          12
Modified Dataframe :
   Experience
0           5
1           7
2          11
3          12

We fetched the column names of dataframe as a sequence and passed the first N column names ( df.columns[:N] ) as the columns argument in drop() function, therefore it deleted the first N columns (3 columns) of dataframe.

Use pop() to remove first N columns of pandas dataframe

In Pandas, dataframe provides a function pop(column_name). It expects a column name as an argument and deletes that column from the calling dataframe object. It also returns the deleted column as a series. We can use this to delete first N column of dataframe, for that we need to iterate over column names of dataframe and for first N columns call pop() function one by one. For example,

import pandas as pd

# List of Tuples
empoyees = [('Jack',    34, 'Sydney',   5) ,
            ('Riti',    31, 'Delhi' ,   7) ,
            ('Aadi',    16, 'London',   11) ,
            ('Mark',    41, 'Delhi' ,   12)]


# Create a DataFrame object
df = pd.DataFrame(  empoyees, 
                    columns=['Name', 'Age', 'City', 'Experience'])

print("Contents of the Dataframe : ")
print(df)

N = 3
# Drop first N columns of dataframe
for i in range(N):
        df.pop(df.columns.values[0])

print("Modified Dataframe : ")
print(df)

Output:

Contents of the Dataframe :
   Name  Age    City  Experience
0  Jack   34  Sydney           5
1  Riti   31   Delhi           7
2  Aadi   16  London          11
3  Mark   41   Delhi          12
Modified Dataframe :
   Experience
0           5
1           7
2          11
3          12

It removed the first 3 columns of dataframe in place.

Use del keyword to remove first N columns of pandas dataframe

Iterate over first N column names of dataframe and for each of them select the column by passing column name in subscript operator i.e. df[df.columns[0]]. Then call del keyword on that selected column.

Checkout complete example to remove the first 3 columns of dataframe,

import pandas as pd

# List of Tuples
empoyees = [('Jack',    34, 'Sydney',   5) ,
            ('Riti',    31, 'Delhi' ,   7) ,
            ('Aadi',    16, 'London',   11) ,
            ('Mark',    41, 'Delhi' ,   12)]


# Create a DataFrame object
df = pd.DataFrame(  empoyees, 
                    columns=['Name', 'Age', 'City', 'Experience'])


print("Contents of the Dataframe : ")
print(df)

N = 3
# Drop first N columns of dataframe
for i in range(N):
        del df[df.columns.values[0]]

print("Modified Dataframe : ")
print(df)

Output:

Contents of the Dataframe :
   Name  Age    City  Experience
0  Jack   34  Sydney           5
1  Riti   31   Delhi           7
2  Aadi   16  London          11
3  Mark   41   Delhi          12
Modified Dataframe :
   Experience
0           5
1           7
2          11
3          12

It deleted the first 3 columns of dataframe in place.

Summary:

We learned about four different ways to delete first N columns of a dataframe.

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