Stop Using .iterrows(). Here's What Actually Fast Looks Like

📰 Dev.to · Iman

Learn why using .iterrows() is slow and how to speed up your pandas DataFrame loops for better performance

intermediate Published 21 May 2026
Action Steps
  1. Use the .apply() function to perform operations on each row or column of a DataFrame
  2. Utilize vectorized operations to perform element-wise calculations on entire DataFrames at once
  3. Leverage the .loc[] accessor to select and manipulate specific rows and columns
  4. Apply NumPy's universal functions to perform efficient element-wise operations
  5. Use Dask DataFrames for parallel computing on large datasets
Who Needs to Know This

Data scientists and analysts who work with large datasets can benefit from this knowledge to improve their code's efficiency and scalability

Key Insight

💡 .iterrows() is slow because it creates a new Series for each row, whereas vectorized operations and other alternatives can process entire DataFrames at once

Share This
💡 Ditch .iterrows() for faster pandas performance! Use .apply(), vectorized ops, .loc[], and NumPy's universal functions instead

Key Takeaways

Learn why using .iterrows() is slow and how to speed up your pandas DataFrame loops for better performance

Full Article

You're looping over a DataFrame. It feels natural. It's killing your performance. # What most...
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