read csv from blob storage with Azure function no permissions

Question

I would like to read csv file from Azure blob storage with python Azure function. Using the code below, I get the error:

[Errno 30] Read-only file system: '/home/site/wwwroot/my_csv_file'

And the code snippet is:

work_directory= os.getcwd()
filename = my_csv_file
account_name = <blob_storage>
account_key = <blob_key>

os.chmod(work_directory, 0o777)

input_fpath=os.path.join(work_directory, filename)
block_blob_service = BlockBlobService(account_name, account_key)
block_blob_service.get_blob_to_path(container_name=<input_container_name>, blob_name=filename,
                                          file_path=input_fpath)

How could I change permissions or how I can read csv to python in other way?

The error shows the error file is in your function disk not the blob file. — George Chen, Oct 28 '19 at 12:46
And in the python function it's default read-only that's why it shows Read-Only. — George Chen, Oct 28 '19 at 14:36
@GeorgeChen I've solved this with block_blob_service.get_blob_to_path(...).content — Mirit, Oct 30 '19 at 14:41
If you solve it, you could post you answer and mark it to close this question. — George Chen, Oct 30 '19 at 14:43
Sorry for the typo: block_blob_service.get_blob_to_*text(...)*.content should be insted of get_blob_to_path — Mirit, Oct 30 '19 at 14:50
And are you sure you could use `chmod` method in the function ? — George Chen, Oct 30 '19 at 14:52
@GeorgeChen Thank you! I've posted my answer and corrected the code. No 'chmod' in this case :) — Mirit, Oct 30 '19 at 14:57

Mirit · Accepted Answer · 2019-10-30T15:00:22.390

SOLVED using get_blob_to_text instead of get_blob_to_path:

blobstring = block_blob_service.get_blob_to_text(<input_container_name>, file_name).content

The solution was found here.

chmod is not required. So, the whole code is the following:

filename = my_csv_file
account_name = <blob_storage>
account_key = <blob_key>

block_blob_service = BlockBlobService(account_name, account_key)
blobstring = block_blob_service.get_blob_to_text(<input_container_name>, filename).content

score 0 · Answer 2 · answered Oct 29 '19 at 09:33

For now the Python Azure function doesn't allow to write the file, it's read-only mode and this is not able to change. So you could neither use chmod method nor use get_blob_to_path cause you could write file to your disk.

So maybe you could read your file to a stream then send it to the response. You could refer to my code, I use the Blob binding to read a text file.

def main(req: func.HttpRequest,inputblob: func.InputStream) -> func.HttpResponse:
logging.info('Python HTTP trigger function processed a request.')

name = req.params.get('name')
if not name:
    try:
        req_body = req.get_json()
    except ValueError:
        pass
    else:
        name = req_body.get('name')

if name:
    return func.HttpResponse(inputblob.read(size=-1))
else:
    return func.HttpResponse(
         "Please pass a name on the query string or in the request body",
         status_code=400
    )

read csv from blob storage with Azure function no permissions

2 Answers2