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How to Speed Up Column Lookups with DataFrame Index in Python

Use pandas set_index to make repeated column value lookups O(1)-style fast instead of scanning the whole DataFrame each time.

pandas indexing performance

Python

import pandas as pd

# Mock dataset with duplicate customer IDs
data = {"customer_id": [101, 102, 103, 101, 104, 102],
        "order_amount": [250.0, 85.5, 300.0, 175.25, 420.0, 95.75]}

df = pd.DataFrame(data)
df = df.set_index("customer_id")

# Simulated lookup request
search_id = 102

# Fast index-based lookup (no…

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