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If you're connecting to buckets hosted at the ECMWF side of the European Weather Cloud, the endpoints are:

• • CCI1 cluster :  https://object-store.os-api.cci1.ecmwf.int 
  • CCI2 cluster : https://object-store.os-api.cci2.ecmwf.int  

import os
import io
import boto3


# Initializing variables for the client 
S3_BUCKET_NAME = "MyFancyBucket123"  #Fill this in  
S3_ACCESS_KEY = "123asdf"  #Fill this in  
S3_SECRET_ACCESS_KEY = "123asdf111"  #Fill this in  
S3_ENDPOINT_URL = "https://my-s3-endpoint.com"  #Fill this in   

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• upload a file into the new bucket (case 3)
• list the contents of the bucket to verify your file is there (case 1)
• download the file you uploaded (case 2)

Related examples

• Streaming large file in Python from s3 bucket.

Other Resources

• Check a more detailed view into boto3's functionality (although it does emphasize on Amazon Web Services specifically, you can take a look at the Python code involved): https://dashbird.io/blog/boto3-aws-python/
• Check out a full code example at the official boto3 website: https://boto3.amazonaws.com/v1/documentation/api/latest/guide/s3-examples.html
• Check a differently styled tutorial at https://towardsdatascience.com/introduction-to-pythons-boto3-c5ac2a86bb63

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