--- title: "How to read a Feather file in Python (faster than pandas)" date: "2026-06-15" author: "Al Brown" category: "Engineering" excerpt: "Read a Feather file into a DataFrame with chDB, a drop-in replacement for pandas. Change one import line and your existing pandas code runs on ClickHouse's engine, so it stays fast as files grow." --- # How to read a Feather file in Python (faster than pandas) To read a Feather file in Python, use [chDB](/resources/engineering/what-is-chdb) as a drop-in replacement for pandas. Change one import line and the code you already write keeps working: ```python import chdb.datastore as pd df = pd.read_feather("events.feather") ``` `df` supports the pandas API you already use (indexing, filtering, `groupby`, `merge`), but the work runs on ClickHouse's engine instead of pandas, so it stays fast as files grow. There is no server to start and no separate load step. ```bash pip install chdb ``` ## Read a Feather file into a DataFrame `pd.read_feather` works the way you expect. Point it at a path and print the result: ```python import chdb.datastore as pd df = pd.read_feather("events.feather") print(df.head(8)) print(df.dtypes) ``` ```text id country event_type quantity amount event_time 0 0 GB cart 8 350.98 1768110393 1 1 IN view 6 830.73 1772107899 2 2 DE cart 10 981.54 1771606592 3 3 DE view 6 528.92 1772725868 4 4 US cart 5 804.15 1774390759 5 5 GB view 9 363.26 1772159477 6 6 IN purchase 10 23.42 1769334173 7 7 US view 10 747.28 1773645610 id uint64 country object event_type object quantity uint8 amount float64 event_time uint32 dtype: object ``` The schema comes from the Arrow footer in the file, so column names and types are read directly. Feather is the on-disk name for Arrow IPC, and chDB reads it with ClickHouse's Arrow reader. One thing is different from pandas under the hood: `df` is not the whole file loaded into memory. It is a lazy, ClickHouse-backed object that records what you asked for and runs it on ClickHouse's engine when you materialize a result, whether you print it, take `len()`, or call `.to_pandas()`. That is why it stays fast on large files: it only computes the rows and columns you actually use. Note that `event_time` came back as `uint32`. This file was written from a ClickHouse `DateTime`, which serializes to Arrow as a 32-bit unsigned epoch. If you need real datetime objects, materialize first and convert: `pandas.to_datetime(pdf["event_time"], unit="s")`. A file written from a pandas datetime column carries an Arrow timestamp type and reads back as a timestamp directly. ## Filter and aggregate the way you already do The pandas you write does not change. Filter with a boolean mask, group, and aggregate: ```python import chdb.datastore as pd df = pd.read_feather("events.feather") revenue = (df[df["event_type"] == "purchase"] .groupby("country")["amount"].sum() .sort_values(ascending=False)) print(revenue.to_pandas()) ``` ```text country GB 100213415.44 US 100120032.40 AU 100062085.37 DE 99909346.62 IN 99687151.84 Name: amount, dtype: float64 ``` Same syntax as pandas, same result. chDB compiles the whole chain into one optimized query and only scans the columns the aggregation touches, rather than materializing the full file first. Joins, computed columns with `assign`, the `.str` and `.dt` accessors, and `merge` across files all work the same way. ## Hand off to real pandas when you need it When a library downstream needs an actual pandas DataFrame (scikit-learn, a plotting call, anything that mutates in place), call `.to_pandas()` to materialize one: ```python df = pd.read_feather("events.feather") pdf = df.to_pandas() # a real pandas.DataFrame, in memory ``` The usual pattern is to do the heavy filtering and aggregation on the chDB object, where it is fast, then `.to_pandas()` the small result and continue in ordinary pandas. ## Is it faster than `pandas.read_feather`? Feather is already a columnar, memory-mappable format, so pandas reads it efficiently and the gap is narrower than it is for row-oriented text formats. The aggregation above on a 3M-row (~68 MB) Feather file, best-of-3 with a warm page cache on an Apple M4 Pro (14 cores, 24 GB RAM, macOS); chDB 4.1.8, Python 3.14; best-of-3, warm: ```text import pandas as pd: 0.051s import chdb.datastore as pd: 0.033s speedup: 1.5x ``` About 1.5x here, from the same code with one import changed. The back-to-back ratio is the robust claim; absolute times shift with cache state and concurrent load. The gap widens as files grow, because chDB scans only the columns and rows the aggregation needs while `pandas.read_feather` reads the full file into a DataFrame before it can group anything. The small case can cut the other way: on a tiny Feather file (a few thousand rows) plain pandas is as fast or faster, because chDB pays a fixed per-query startup cost that dominates when there is barely any data. Reach for chDB when the file is large, or when you want one import to cover both. ## Works in Jupyter Printing a chDB object renders it as a table in a notebook, and `.to_pandas()` feeds straight into `.plot()`, joins, or any pandas code. The companion folder ships a `run.ipynb` you can open and run cell by cell. ## Run it yourself The complete, runnable example is here, with `generate.sh` to create the sample Feather file plus `run.ipynb` and a `run.py` mirror containing the exact code above: [github.com/ClickHouse/examples/tree/main/local-analytics/chdb-feather](https://github.com/ClickHouse/examples/tree/main/local-analytics/chdb-feather) Working with other formats? [Read an Arrow file in Python](/resources/engineering/read-arrow-file-python) uses the same reader since Feather and Arrow IPC are the same format. [Read a Parquet file in Python](/resources/engineering/read-parquet-file-python) and [read a CSV file in Python](/resources/engineering/read-csv-file-python) use the same `import chdb.datastore as pd` pattern; only the reader changes. The same code scales from a file on your laptop to a server to [ClickHouse Cloud](https://clickhouse.com/cloud) with no rewrite, so there is nothing to re-learn when the data outgrows one machine.