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Iterrows

As explained in Fast Python: High performance techniques for large datasets

iterrows is a pandas DataFrame method that yields row index and row data pairs for sequential row traversal.

iterrows traverses a pandas DataFrame with a for loop, yielding each row’s current position and row data. It offers a familiar baseline, but remains slow for substantial computations. section 7.2.2

Use iterrows cautiously when working with row-oriented logic:

  • Expect only a slight improvement over explicit indexing; both approaches can take minutes. section 7.2.2
  • Prefer itertuples when a loop is unavoidable; the same calculation falls to about 18 seconds in the comparison. section 7.2.2
  • Move toward apply or vectorization for row calculations; apply reaches 9.5 seconds, while vectorization avoids row-wise iteration. section 7.2.2
def get_tip_mean_iterrows(df):
    all_tips = 0
    all_totals = 0
    for i, row in df.iterrows():
        all_tips += row["tip_amount"]
        all_totals += row["total_amount"]
    return all_tips / all_totals

A minimal iterrows implementation computes aggregate tip and total amounts while exposing the iterator’s index-and-row interface. section 7.2.2

How Fast Python: High performance techniques for large datasets covers it

How deep it goes
Defines the yielded index-and-row interface and benchmarks performance, but does not explain iterator internals.
Examples
Demonstrates tip-to-total aggregation over sampled taxi-trip DataFrames and compares several row-processing implementations.
What it assumes
Assumes familiarity with pandas DataFrames, columns, row calculations, and Python for loops.
What you can do after
Evaluate row-iteration performance and choose itertuples, apply, or vectorization when iterrows is too slow.
How it connects
Connects iterrows with pandas DataFrames, explicit iteration, itertuples, apply, and vectorization.

Related concepts

This explainer was generated by Manning's knowledge graph from the text of Fast Python: High performance techniques for large datasets. The section links point to the parts of the book it draws on.