Adding and Modifying Columns

Adding and Modifying Columns

import pandas as pd
df = pd.read_csv('data.csv')

# Add column
df['full_name'] = df['first_name'] + ' ' + df['last_name']
df['is_senior'] = df['age'] >= 60
df['tax'] = df['price'] * 0.1

# Apply a function
df['name_upper'] = df['name'].str.upper()
df['score_grade'] = df['score'].apply(
    lambda x: 'A' if x >= 90 else 'B' if x >= 80 else 'C'
)

# Map values
status_map = {'active': 1, 'inactive': 0, 'banned': -1}
df['status_code'] = df['status'].map(status_map)

# pd.cut — bin numeric into categories
df['age_group'] = pd.cut(df['age'],
    bins=[0, 18, 35, 60, 100],
    labels=['teen', 'young', 'middle', 'senior'])

# Drop column
df.drop(columns=['old_col'], inplace=True)