How to Add a New Column to an Existing Pandas Dataframe?
To add a new column to an existing pandas dataframe, you can simply assign a new column to the dataframe using the indexing operator [] or the assign() method.
Here are two ways to add a new column to a pandas dataframe:
# Example dataframe
import pandas as pd
data = {'name': ['John', 'Emma', 'Peter', 'Lucy'], 'age': [25, 30, 35, 40]}
df = pd.DataFrame(data)
# Method 1: Using indexing operator []
df['gender'] = ['Male', 'Female', 'Male', 'Female']
print(df)
# Method 2: Using assign() method
df = df.assign(salary=[50000, 60000, 70000, 80000])
print(df)
Output:
# Method 1
name age gender
0 John 25 Male
1 Emma 30 Female
2 Peter 35 Male
3 Lucy 40 Female
# Method 2
name age salary
0 John 25 50000
1 Emma 30 60000
2 Peter 35 70000
3 Lucy 40 80000
The first method adds a new column 'gender' to the dataframe by assigning a list of values to it. The second method uses the assign() method to create a new column 'salary' with a list of values. Both methods reflect the new columns in the dataframe.