如何使用 csv.DictReader 读取存储在 S3 中的 csv？

Question

我有获取 AWS S3 对象的代码。如何使用 Python 的 csv.DictReader 读取这个 StreamingBody？

import boto3, csv

session = boto3.session.Session(aws_access_key_id=<>, aws_secret_access_key=<>, region_name=<>)
s3_resource = session.resource('s3')
s3_object = s3_resource.Object(<bucket>, <key>)
streaming_body = s3_object.get()['Body']

#csv.DictReader(???)

Answer 1

代码是这样的：

import boto3
import csv

# get a handle on s3
s3 = boto3.resource(u's3')

# get a handle on the bucket that holds your file
bucket = s3.Bucket(u'bucket-name')

# get a handle on the object you want (i.e. your file)
obj = bucket.Object(key=u'test.csv')

# get the object
response = obj.get()

# read the contents of the file and split it into a list of lines

# for python 2:
lines = response[u'Body'].read().split()

# for python 3 you need to decode the incoming bytes:
lines = response['Body'].read().decode('utf-8').split()

# now iterate over those lines
for row in csv.DictReader(lines):

    # here you get a sequence of dicts
    # do whatever you want with each line here
    print(row)

您可以在实际代码中稍微压缩一下，但我尝试逐步保持它以使用 boto3 显示对象层次结构。

根据您关于避免将整个文件读入内存的评论进行编辑：我没有遇到这个要求，所以不能权威地说，但我会尝试包装流，这样我就可以获得一个文本文件- 类似迭代器。例如，您可以使用 codecs 库将上面的 csv 解析部分替换为：

for row in csv.DictReader(codecs.getreader('utf-8')(response[u'Body'])):
    print(row)