How to De‑duplicate Billions of Rows in Python Without Running Out of Memory

1. Introduction

In a Python community, a user asked how to filter rows that appear at least 1,000 times in a dataset of 500 million rows, a task that previously caused memory overflow.

2. Implementation

One suggestion was to use a specific approach (shown below):

Another approach combined tuples with a set, and later fans used a merge‑by‑union method to solve the problem.

A third attempt concatenated all data and applied drop_duplicates, which also led to memory explosion.

3. Summary

The article reviews a big‑data deduplication issue, presents concrete analysis and code solutions, and thanks the contributors.

It also advises how to ask questions about large files: anonymize data, provide small demo samples, include error screenshots, and share code directly or as a .py file if longer than 50 lines.