The apply() Function

The apply() function lets you apply custom functions to rows, columns, or individual elements.

Apply to Columns

Apply a function to each column:

Apply to Rows

Use axis=1 to apply across rows:

Lambda Functions

Use lambda for simple operations:

Apply with Multiple Arguments

Pass additional arguments to your function:

applymap() for Element-wise

Apply function to every element:

Apply vs Vectorized Operations

Vectorized operations are usually faster:

Exercise: Custom Calculation

Exercise: Transform Values

Key Points

• apply(func) applies function to columns (axis=0)
• apply(func, axis=1) applies to rows
• Lambda functions for simple transformations
• Pass extra args via lambda or using args=
• Vectorized operations are faster when possible
• Use apply when you need complex logic