Combine all txt files in an S3 bucket into 1 large file - amazon-web-services

Question

Problem: I am trying to combine large amounts of small-sized text files into 1 large-sized file in S3 bucket. Using python:
The code I tested to try this locally is below. It works perfectly. (obtained from another post):
with open(outfilename, 'wb') as outfile:
for filename in glob.glob('UBXEvents*'):
if filename == outfilename: # don't want to copy the output into the output
continue
with open(filename, 'rb') as readfile:
shutil.copyfileobj(readfile, outfile)
Now, since my files are located in an S3 bucket, I have trouble referencing the S3 bucket. I wanted to run this code for all files (using wild card *) in an S3 but I am having a hard time connecting the two.
Below is the s3 object I created:
object = client.get_object(
Bucket= 'my_bucket_name',
Key='bucket_path/prefix_of_file_name*'
)
Question: How would I reference the S3 bucket/path in my combining code above?

Answer 1

Obtaining a list of files
You can obtain a list of files in the bucket like this:
import boto3
s3_client = boto3.client('s3')
response = s3_client.list_objects_v2(Bucket='my-bucket', Prefix = 'folder1/')
for object in response['Contents']:
# Do stuff here
print(object['Key'])
Reading & Writing to Amazon S3
Normally, you would need to download each file from Amazon S3 to the local disk (using download_file() and then read the contents). However, you might instead want to use smart-open · PyPI, which is a library that allows files to be opened on S3 using similar syntax to the normal Python open() command.
Here's a program that uses smart-open to read files from S3 and combine them into an output file in S3:
import boto3
from smart_open import open
BUCKET = 'my-bucket'
PREFIX = 'folder1/' # Optional
s3_client = boto3.client('s3')
# Open output file with smart-open
with open(f's3://{BUCKET}/out.txt', 'w') as out_file:
response = s3_client.list_objects_v2(Bucket=BUCKET, Prefix = PREFIX)
for object in response['Contents']:
print(f"Copying {object['Key']}")
# Open input file with smart-open
with open(f"s3://{BUCKET}/{object['Key']}", 'r') as in_file:
# Read content from input file
for line in in_file:
# Write content to output file
out_file.write(line)