How to Read a Folder of CSVs in Python Using DuckDB

2 min

As we find ourselves in the era of Big Data, the ability to effectively and efficiently handle large datasets is a crucial skill for any data professional. In today's post, we'll be exploring a practical and effective way of reading a folder of CSVs in Python using DuckDB, an open-source analytical database management system.

Key Takeaways:

  1. Introduction to DuckDB, an efficient open-source analytical database system.
  2. The efficiency and benefits of using DuckDB over traditional methods such as Pandas.
  3. A practical guide to reading a directory of CSVs using DuckDB in Python.

What is DuckDB?

DuckDB is an open-source analytical database system written in C++. It is a column-oriented database system, meaning it's optimized for analytical queries, making it ideal for Big Data applications. DuckDB is designed to support complex queries over large datasets, while still maintaining a small memory footprint and a straightforward API, making it a powerful tool for data analysis.

Why Use DuckDB?

There are several reasons why DuckDB is a powerful tool for data processing:

  1. Performance: DuckDB is optimized for analytical queries, providing fast query execution over large datasets.
  2. Versatility: DuckDB supports SQL queries, allowing users to leverage the full power of SQL when processing data.
  3. Efficiency: DuckDB has a small memory footprint, making it an excellent choice for applications with limited memory resources.

DuckDB vs. Pandas : A comparison

While Pandas is a fantastic library for data manipulation and analysis, it's not always the best tool for handling large datasets. This is where DuckDB shines.

When processing large volumes of data, Pandas can be slow and consume a considerable amount of memory. On the other hand, DuckDB's column-oriented design allows it to process data more efficiently, providing faster execution times, and handling larger datasets than Pandas with less memory usage.

Moreover, DuckDB also provides support for SQL, a well-established and powerful language for data analysis, making it an appealing alternative to raw Pandas for large-scale data processing tasks.

A Practical Guide to Reading a Directory of CSVs using DuckDB in Python

Now, let's get to the heart of this post: reading a directory of CSVs using DuckDB in Python.

Firstly, let's import DuckDB and establish a connection to the database.

import duckdb

# establish a connection to DuckDB
conn = duckdb.connect('database.db')

Next, we will use the read_csv_auto function, which automatically detects CSV files in a directory and registers it as a table:

# register the CSV directory as a table
df = conn.execute("""
        SELECT *
        FROM read_csv_auto('data/*.csv', header=True)

We can then print the dataframe and finally close the connection:


# close the connection

And voilà! You have just read a folder of CSVs using DuckDB in Python.


In conclusion, DuckDB presents a compelling alternative to traditional data processing methods such as Pandas. With its column-oriented design and SQL support, it provides an efficient and powerful tool for processing large datasets. By combining it with Python, one of the most popular languages for data analysis, you can easily handle and process a multitude of CSVs, allowing you to tackle even the most challenging data processing tasks.

Remember to keep exploring, keep learning, and as always, happy data crunching!