GCSFS

A Python filesystem abstraction of Google Cloud Storage (GCS) implemented as a PyFilesystem2 extension.

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With GCSFS, you can interact with Google Cloud Storage as if it was a regular filesystem.

Apart from the nicer interface, this will highly decouple your code from the underlying storage mechanism: Exchanging the storage backend with an in-memory filesystem for testing or any other filesystem like S3FS becomes as easy as replacing gs://bucket_name with mem:// or s3://bucket_name.

For a full reference on all the PyFilesystem possibilities, take a look at the PyFilesystem Docs!

Installing

Install the latest GCSFS version by running:

$ pip install fs-gcsfs

Or in case you are using conda:

$ conda install -c conda-forge fs-gcsfs

Examples

Instantiating a filesystem on Google Cloud Storage (for a full reference visit the Documentation):

from fs_gcsfs import GCSFS
gcsfs = GCSFS(bucket_name="mybucket")

Alternatively you can use a FS URL to open up a filesystem:

from fs import open_fs
gcsfs = open_fs("gs://mybucket/root_path?strict=False")

You can use GCSFS like your local filesystem:

>>> from fs_gcsfs import GCSFS
>>> gcsfs = GCSFS(bucket_name="mybucket")
>>> gcsfs.tree()
├── foo
│   ├── bar
│   │   ├── file1.txt
│   │   └── file2.csv
│   └── baz
│       └── file3.txt
└── file4.json
>>> gcsfs.listdir("foo")
["bar", "baz"]
>>> gcsfs.isdir("foo/bar")
True

Uploading a file is as easy as:

from fs_gcsfs import GCSFS
gcsfs = GCSFS(bucket_name="mybucket")
with open("local/path/image.jpg", "rb") as local_file:
    with gcsfs.open("path/on/bucket/image.jpg", "wb") as gcs_file:
        gcs_file.write(local_file.read())

You can even sync an entire bucket on your local filesystem by using PyFilesystem’s utility methods:

from fs_gcsfs import GCSFS
from fs.osfs import OSFS
from fs.copy import copy_fs

gcsfs = GCSFS(bucket_name="mybucket")
local_fs = OSFS("local/path")

copy_fs(gcsfs, local_fs)

For exploring all the possibilities of GCSFS and other filesystems implementing the PyFilesystem interface, we recommend visiting the official PyFilesystem Docs!

Development

To develop on this project make sure you have pipenv installed and run the following from the root directory of the project:

$ pipenv install --dev --three

This will create a virtualenv with all packages and dev-packages installed.

Tests

All CI tests run against an actual GCS bucket provided by Othoz. In order to run the tests against your own bucket, make sure to set up a Service Account with all necessary permissions:

  • storage.buckets.get
  • storage.objects.get
  • storage.objects.list
  • storage.objects.create
  • storage.objects.update
  • storage.objects.delete

Expose your bucket name as an environment variable $TEST_BUCKET and run the tests via:

$ pipenv run pytest

Note that the tests mostly wait for I/O, therefore it makes sense to highly parallelize them with xdist.

Credits

Credits go to S3FS which was the main source of inspiration and shares a lot of code with GCSFS.

Limitations

A filesystem built on top of an object store like GCS suffers from the same limitations as the ones mentioned in S3FS.

GCS does not offer true directories which is why GCSFS (as well as S3FS) will simulate the existence of a directory called foo by adding an empty blob called foo/. Any filesystem content that was not created via GCSFS will lack these directory markers which may lead to wrong behaviour. For example gcsfs.isdir("bar") will return False if the marker blob bar/ does not exist, even though there might exist a blob called bar/baz.txt.

To overcome this you can call the utility method fix_storage() on your GCSFS instance which will walk the entire filesystem (i.e. the entire bucket or the “subdirectory” you specified via root_path) and add all missing directory markers.

Warning

Listing and fixing large buckets may take some time!

Reference

For a full reference of all available methods of GCSFS visit the documentation of fs.base.FS!

class fs_gcsfs.GCSFS(bucket_name: str, root_path: str = None, create: bool = False, client: google.cloud.storage.client.Client = None, strict: bool = True)

A GCS filesystem for PyFilesystem

This implementation is based on S3FS

Args:

bucket_name: The GCS bucket name. root_path: The root directory within the GCS Bucket create: Whether to create root_path on initialization or not. If root_path does not yet exist and create=False a CreateFailed

exception will be raised. To disable root_path validation entirely set strict=False.

client: A google.storage.Client exposing the google storage API. strict: When True (default) GCSFS will follow the PyFilesystem specification exactly. Set to False to disable validation of destination paths

which may speed up some operations.
fix_storage() → None

Utility function that walks the entire root_path and makes sure that all intermediate directories are correctly marked with empty blobs.

As GCS is no real file system but only a key-value store, there is also no concept of folders. S3FS and GCSFS overcome this limitation by adding empty files with the name “<path>/” every time a directory is created, see https://fs-gcsfs.readthedocs.io/en/latest/#limitations.

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This PyFilesystem extension was created by Othoz GmbH