4. Iteration & Basic Loops

Loop through columns or rows.

• df.__iter__ → Dunder method for iterating over columns (not used directly).
• df.items() → Iterate over (column_name, Series) pairs.
• df.keys() → Alias for df.columns; returns column labels.
• df.iterrows() → Iterate over (index, row Series) pairs; convenient but slower.
• df.itertuples() → Iterate rows as namedtuples; faster than iterrows.

Iteration & Basic Loops in Pandas DataFrames

Performance Warning ⚠️

Before we begin: Vectorized operations are almost always faster than iteration in pandas. Use these methods only when absolutely necessary.