Adding & Modifying Columns

Creating new columns and updating existing ones are fundamental DataFrame operations.

Adding a New Column

Assign values to a new column name:

Calculations Between Columns

Perform operations using multiple columns:

Conditional Column Values

Use conditions to set values:

Modifying Existing Columns

Update values in place:

Using assign() Method

Create columns without modifying original:

Insert Column at Specific Position

Use insert() to place column at an index:

Exercise: Calculate Tax

Exercise: Conditional Status

Key Points

• df['new_col'] = values adds a column
• Columns can be calculated from other columns
• np.where() for if-else conditions
• np.select() for multiple conditions
• assign() creates columns without modifying original
• insert(pos, name, values) for specific position