google.appengine.ext.blobstore.fetch_data_async

Asynchronously fetches data for a blob.

View aliases

Main aliases

`google.appengine.ext.blobstore.blobstore.fetch_data_async`

google.appengine.ext.blobstore.fetch_data_async(
    blob, start_index, end_index, rpc=None
)

Fetches a fragment of a blob up to MAX_BLOB_FETCH_SIZE in length. Attempting to fetch a fragment that extends beyond the boundaries of the blob will return the amount of data from start_index until the end of the blob, which will be a smaller size than requested. Requesting a fragment that is entirely outside the boundaries of the blob will return an empty string. Attempting to fetch a negative index will raise an exception.

Args
blob	A BlobInfo, BlobKey, string, or Unicode representation of the BlobKey of the blob from which you want to fetch data.
start_index	The start index of blob data to fetch. This value must not be negative.
end_index	The end index (inclusive) of the blob data to fetch. This value must be greater than or equal to start_index.
rpc	Optional UserRPC object.

Returns
A UserRPC whose result will be a string as returned by fetch_data().

Raises
TypeError	If start_index or end_index are not indexes, or if blob is not a string, BlobKey or BlobInfo.
DataIndexOutOfRangeError	If start_index is set to a value that is less than 0 or end_index is less than start_index when calling rpc.get_result().
BlobFetchSizeTooLargeError	If the requested blob fragment is larger than MAX_BLOB_FETCH_SIZE when calling rpc.get_result().
BlobNotFoundError	If the blob does not exist when calling rpc.get_result().