ImportError: cannot import name 'BlockBlobService' from 'azure.storage.blob'
Fixes legacy v2-track code running against azure-storage-blob v12, which removed BlockBlobService. Use when old samples fail on a fresh install. Not for v2-installed environments.
TL;DR: BlockBlobService was the v2-track client and v12 deleted it. Either migrate to BlobServiceClient (recommended) or pin azure-storage-blob<3 to keep the old API.
ImportError: cannot import name 'BlockBlobService' from 'azure.storage.blob'Fix it
- Decide: migrate or pin. Migrating is better for anything you will maintain.
- To migrate: pip install -U azure-storage-blob, then replace BlockBlobService(connectionstring=...) usage with BlobServiceClient.fromconnection_string(...), and method calls per the v12 migration guide. Expected: imports succeed.
- To pin (short-term only): pip install "azure-storage-blob<3". Expected: BlockBlobService imports again.
- Record the choice in requirements so the next fresh install is deterministic.
When this applies
- The code imports BlockBlobService and pip shows azure-storage-blob 12.x.
When it doesn't
- pip shows 2.x and the import still fails: namespace conflict; see the azure.identity namespace skill.
- You are writing new code: use BlobServiceClient from the start.
Compatibility
- v12: azure-storage-blob >= 12.0. Legacy: azure-storage-blob 2.x.
Why it happens
Major-version SDK rewrites drop old classes. v12 kept the package name but replaced the entire surface, so old imports fail loudly instead of subtly.
Edge cases
- Some third-party libraries still import BlockBlobService internally; pinning may be forced until they migrate.
- Connection strings from the portal work with both tracks, so auth config does not need to change.
Maintainer review
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