AzureBlob Upload ERROR:The specified blob already exists


I am trying to upload file to Azure container daily.

I got an Error:”The specified blob already exists” when uploading file with same file( I want to overwrite the file)

from import BlobServiceClient, BlobClient, ContainerClient

conn_str = yml['AZURE_BLOB']['CONN_STR']
container_name = yml['AZURE_BLOB']['CONTAINER_NAME']

# Create the BlobServiceClient that is used to call the Blob service for the storage account
blob_service_client = BlobServiceClient.from_connection_string(conn_str=conn_str)

# Create a blob client using the local file name as the name for the blob
blob_client = blob_service_client.get_blob_client(container=container_name, blob=destination_file_name)

# Upload the created file
data =,mode='rb').read()


Error message:

azure.core.exceptions.ResourceExistsError: The specified blob already exists.
Asked By: EEEEH



Check out this blog post about a known issue.

This is a known issue with development storage. This happens when there are multiple threads launched to upload the blocks (which constitute the blob). Basically what is happening is that development storage makes use of SQL Server as the data store. Now first thing it does is makes an entry into the table which stores blob information. If there are multiple threads working then all of these threads will try to perform the same operation. After the first thread succeeds, the subsequent threads will result in this exception being raised.

Answered By: furkanayd

If you want to overwrite the existing blob using Blob storage client library v12, just add overwrite=True in the upload_blob method.

Here is the sample code:

from import BlobServiceClient, BlobClient, ContainerClient

conn_str = "xxx"
container_name = "test6"

blob_service_client = BlobServiceClient.from_connection_string(conn_str=conn_str)
blob_client = blob_service_client.get_blob_client(container=container_name,blob="a1.txt")

with open("F:\temp\a1.txt","rb") as data:


After executing the code, the new blob is uploaded and the existing blob can be overwritten. Screenshot as below:

enter image description here

Answered By: Ivan Yang