Prescrape

Prescrape is a term used in data extraction and web scraping to describe the process of collecting data from a website *before* a specific event occurs or a particular condition is met. This contrasts with scraping that happens after the event or condition, or continuous scraping. The primary purpose of prescraping is often to establish a baseline, gather historical data, or collect information that might be difficult or impossible to obtain later.

For instance, in e-commerce, a prescrape might be performed on product prices before a major sale event begins. This allows for later comparison to analyze the sale's effectiveness or to understand how prices fluctuated. In financial markets, prescraping might involve collecting stock prices or trading volumes before a significant news announcement. This data can then be used to study the market's reaction to the news.

The implementation of prescraping requires careful planning to identify the exact moment or condition that triggers the data collection. It often involves scheduling or setting up automated scripts to run at precisely the right time. Challenges can include the dynamic nature of websites, potential blocks from anti-scraping measures, and the sheer volume of data that might need to be stored. Despite these challenges, prescraping is a valuable technique for researchers, analysts, and businesses seeking to gain insights from data in a temporal context.