How to read a list of parquet files from S3 as a pandas dataframe using pyarrow?

Question

I have a hacky way of achieving this using boto3 (1.4.4), pyarrow (0.4.1) and pandas (0.20.3).

First, I can read a single parq

Answer 1

Thanks! Your question actually tell me a lot. This is how I do it now with pandas (0.21.1), which will call pyarrow, and boto3 (1.3.1).

import boto3
import io
import pandas as pd

# Read single parquet file from S3
def pd_read_s3_parquet(key, bucket, s3_client=None, **args):
    if s3_client is None:
        s3_client = boto3.client('s3')
    obj = s3_client.get_object(Bucket=bucket, Key=key)
    return pd.read_parquet(io.BytesIO(obj['Body'].read()), **args)

# Read multiple parquets from a folder on S3 generated by spark
def pd_read_s3_multiple_parquets(filepath, bucket, s3=None, 
                                 s3_client=None, verbose=False, **args):
    if not filepath.endswith('/'):
        filepath = filepath + '/'  # Add '/' to the end
    if s3_client is None:
        s3_client = boto3.client('s3')
    if s3 is None:
        s3 = boto3.resource('s3')
    s3_keys = [item.key for item in s3.Bucket(bucket).objects.filter(Prefix=filepath)
               if item.key.endswith('.parquet')]
    if not s3_keys:
        print('No parquet found in', bucket, filepath)
    elif verbose:
        print('Load parquets:')
        for p in s3_keys: 
            print(p)
    dfs = [pd_read_s3_parquet(key, bucket=bucket, s3_client=s3_client, **args) 
           for key in s3_keys]
    return pd.concat(dfs, ignore_index=True)

Then you can read multiple parquets under a folder from S3 by

df = pd_read_s3_multiple_parquets('path/to/folder', 'my_bucket')

(One can simplify this code a lot I guess.)