Fastparquet 在使用 dataframe.to_parquet() 时给出“TypeError：预期的 str、字节或 os.PathLike 对象，而不是 _io.BytesIO”

Posted 2023-03-11

【中文标题】Fastparquet 在使用 dataframe.to_parquet() 时给出“TypeError：预期的 str、字节或 os.PathLike 对象，而不是 _io.BytesIO”

【英文标题】：Fastparquet giving "TypeError: expected str, bytes or os.PathLike object, not _io.BytesIO" while using dataframe.to_parquet()

【发布时间】：2020-08-05 11:24:07

【问题描述】：

我正在尝试为 AWS Lambda 创建代码以将 csv 转换为 parquet。我可以使用 Pyarrow 做到这一点，但它的大小太大（未压缩约 200 MB），因此我无法在 Lambda 的部署包中使用它。我正在尝试使用 BytesIO 库直接将镶木地板文件写入 s3 存储桶。

下面是我的 lambda 函数代码：

import json
import boto3
import pandas as pd
from io import BytesIO


def lambda_handler():

    s3 = boto3.client('s3')
    response = s3.list_objects_v2(
        Bucket = 'mybucket',
        Prefix = 'subfolder/'
    )
    files = get_object_keys(response)
    for file in files:
        obj = s3.get_object(Bucket='mybucket', Key=file)
        df = pd.read_csv(obj['Body'], sep='|')


        buf = BytesIO()
        df.to_parquet(buf, engine='fastparquet', index=False, compression='snappy')
        buf.seek(0)
        key = f"output/file.split('/')[1].split('.')[0].parquet"
        s3.put_object(Bucket='mybucket', Body=buf.getvalue(), Key=key)

def get_object_keys(response):

    files = []
    for content in response['Contents']:
        if content['Key'].endswith('.csv'):
            files.append(content['Key'])
    return files

lambda_handler()

当我在 dataframe.to_parquet() 中使用“fastparquet”作为引擎时，出现以下错误：

Traceback (most recent call last):
  File ".\lambda_function.py", line 77, in <module>
    lambda_handler()
  File ".\lambda_function.py", line 64, in lambda_handler
    df.to_parquet(buf, engine='fastparquet', index=False, compression='snappy')
  File "C:\Users\tansingh\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\util\_decorators.py", line 214, in wrapper
    return func(*args, **kwargs)
  File "C:\Users\tansingh\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\core\frame.py", line 2116, in to_parquet  
    **kwargs,
  File "C:\Users\tansingh\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\io\parquet.py", line 264, in to_parquet
    **kwargs,
  File "C:\Users\tansingh\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\io\parquet.py", line 185, in write
    **kwargs,
  File "C:\Users\tansingh\AppData\Local\Programs\Python\Python37\lib\site-packages\fastparquet\writer.py", line 880, in write       
    compression, open_with, has_nulls, append)
  File "C:\Users\tansingh\AppData\Local\Programs\Python\Python37\lib\site-packages\fastparquet\writer.py", line 734, in write_simple
    with open_with(fn, mode) as f:
  File "C:\Users\tansingh\AppData\Local\Programs\Python\Python37\lib\site-packages\fastparquet\util.py", line 42, in default_open   
    return open(f, mode)
TypeError: expected str, bytes or os.PathLike object, not _io.BytesIO

有谁知道如何解决这个问题？

【参考方案1】：

使用pyarrow作为编写引擎解决了这个错误。

示例代码。

buffer = ioBytesIO()
df.to_parquet(buffer, engine="pyarrow", index = False)
s3_resource = boto3.resource('s3')
s3_resouce.Object(`bucketname`, `path_withfilename`).put(body = buffer.getvalue())

为了在 python 3.6 中读取 parquet 文件，我使用了 fastparquet，但对于编写 pyarrow 引擎似乎可以工作。