Python - Add a zero column to Pandas DataFrame

To add a zero column to a Pandas DataFrame, you can use square bracket notation to create a new column and assign 0 to all rows. This is useful for initializing placeholder columns or creating default values.

Creating the DataFrame

First, let's create a sample DataFrame with student data ?

import pandas as pd

# Create DataFrame
dataFrame = pd.DataFrame({
    "Student": ['Jack', 'Robin', 'Ted', 'Marc', 'Scarlett', 'Kat', 'John'],
    "Result": ['Pass', 'Fail', 'Pass', 'Fail', 'Pass', 'Pass', 'Pass'],
    "Roll Number": [5, 10, 3, 8, 2, 9, 6]
})

print("Original DataFrame:")
print(dataFrame)

Original DataFrame:
    Student Result  Roll Number
0      Jack   Pass            5
1     Robin   Fail           10
2       Ted   Pass            3
3      Marc   Fail            8
4  Scarlett   Pass            2
5       Kat   Pass            9
6      John   Pass            6

Adding a Zero Column

Now we'll add a new column filled with zeros using square bracket notation ?

import pandas as pd

# Create DataFrame
dataFrame = pd.DataFrame({
    "Student": ['Jack', 'Robin', 'Ted', 'Marc', 'Scarlett', 'Kat', 'John'],
    "Result": ['Pass', 'Fail', 'Pass', 'Fail', 'Pass', 'Pass', 'Pass'],
    "Roll Number": [5, 10, 3, 8, 2, 9, 6]
})

# Add a zero column
dataFrame['ZeroColumn'] = 0

print("DataFrame with Zero Column:")
print(dataFrame)

DataFrame with Zero Column:
    Student Result  Roll Number  ZeroColumn
0      Jack   Pass            5           0
1     Robin   Fail           10           0
2       Ted   Pass            3           0
3      Marc   Fail            8           0
4  Scarlett   Pass            2           0
5       Kat   Pass            9           0
6      John   Pass            6           0

Alternative Methods

You can also use assign() method for functional programming style ?

import pandas as pd

dataFrame = pd.DataFrame({
    "Student": ['Jack', 'Robin', 'Ted'],
    "Result": ['Pass', 'Fail', 'Pass']
})

# Using assign() method
dataFrame_new = dataFrame.assign(ZeroColumn=0)
print(dataFrame_new)

  Student Result  ZeroColumn
0    Jack   Pass           0
1   Robin   Fail           0
2     Ted   Pass           0

Conclusion

Adding a zero column to a Pandas DataFrame is straightforward using dataFrame['column_name'] = 0. This method directly modifies the original DataFrame, while assign() returns a new DataFrame with the added column.