How to delete blob using SAS token for folder

Question

Hi All,

I am using python SDK for my azure related operations. When I had container level permission for blob, I used the following code

def delete_blobs(asset_name, container_client, file_name, site_name, file_type):

if file_type == 'txt':

    blob_name_dir = f"container/Document/Chunks/{file_name}"

elif file_type == 'pdf':

    blob_name_dir = f"container/Document/Pages/{file_name}"

else:

    logger.info(f"Unsupported file type: {file_type}")

    return

blob_list = container_client.list_blobs(name_starts_with=blob_name_dir)

blob_to_delete = [blob.name for blob in blob_list if blob.name.startswith(blob_name_dir)]

for blob_name in blob_to_delete:

    logger.info(f"Deleting blob: {blob_name}")

    blob_client = container_client.get_blob_client(blob=blob_name)

    blob_client.delete_blob()

    logger.info("Blob got deleted")  

but now my container level permission is removed and SAS token is provided only for the folder

I am using BlobClient.from_blob_url method to access folder but cannot find any of the methods used a blob container. what is the way to search the blob files with starts with and also how can I delete as I am getting permission error for everything now

Answer 1

Hi @Dutta, Pijush

Thank you for posting this in Microsoft Q&A.

You are facing a permission restriction where you can only access a specific folder in an Azure Blob Storage container using a SAS token. Your previous approach using container_client.list_blobs() is no longer feasible due to the limited permissions.

Here’s a sample code snippet

def delete_blobs(sas_token, container_name, folder_path, prefix=None):
    """Deletes blobs within a specified folder using a SAS token.

    Args:
        sas_token: The SAS token for the folder.
        container_name: The name of the container.
        folder_path: The path to the folder within the container.
        prefix: Optional prefix for filtering blobs.
    """

    base_url = f"https://{container_name}.blob.core.windows.net/{folder_path}"
    sas_url = f"{base_url}?{sas_token}"

    blob_client = BlobClient.from_blob_url(sas_url)

    blobs_to_delete = []
    for blob in blob_client.list_blobs_flat():
        if prefix and not blob.name.startswith(prefix):
            continue
        blobs_to_delete.append(blob.name)

    for blob_name in blobs_to_delete:
        blob_client = BlobClient.from_blob_url(f"{sas_url}/{blob_name}")
        blob_client.delete_blob()

I hope this helps!
Please mark as "Accept the answer" if the above steps helps you. Your suggestion will help others also!

Answer 2

Hi @Dutta, Pijush

You can try this alternative approach.

Iterating through hierarchical listings
The list_blobs() offered by the BlobServiceClient or ContainerClient accepts a prefix argument. You can use this argument iteratively to navigate through the container hierarchy and list all blobs.

Here's an example:

def list_blobs_flat(container_client, prefix=""):
#Lists all blobs recursively within a container (flattened)
blobs = [] 
for
blobs.append(blob) 
if
blobs.extend(list_blobs_flat(container_client, blob.name + "/"))
return blobs

I hope this helps!
Don't forget to "Accept the answer" if the above steps helps you. Your suggestion will help others also!

Thanks