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PetrelBackend

class mmengine.fileio.PetrelBackend(path_mapping=None, enable_mc=True, conf_path=None)[source]

Petrel storage backend (for internal usage).

PetrelBackend supports reading and writing data to multiple clusters. If the file path contains the cluster name, PetrelBackend will read data from specified cluster or write data to it. Otherwise, PetrelBackend will access the default cluster.

Parameters
  • path_mapping (dict, optional) – Path mapping dict from local path to Petrel path. When path_mapping={'src': 'dst'}, src in filepath will be replaced by dst. Defaults to None.

  • enable_mc (bool, optional) – Whether to enable memcached support. Defaults to True.

  • conf_path (str, optional) – Config path of Petrel client. Default: None. New in version 0.3.3.

Examples

>>> backend = PetrelBackend()
>>> filepath1 = 'petrel://path/of/file'
>>> filepath2 = 'cluster-name:petrel://path/of/file'
>>> backend.get(filepath1)  # get data from default cluster
>>> client.get(filepath2)  # get data from 'cluster-name' cluster

Create a symbolic link pointing to src named dst.

Directly copy src to dst because PetrelBacekend does not support create a symbolic link.

Parameters
  • src (str or Path) – A file or directory to be copied.

  • dst (str or Path) – Copy a file or directory to dst.

  • backend_args (dict, optional) – Arguments to instantiate the prefix of uri corresponding backend. Defaults to None.

Returns

Return False because PetrelBackend does not support create a symbolic link.

Return type

bool

Examples

>>> backend = PetrelBackend()
>>> src = 'petrel://path/of/file'
>>> dst = 'petrel://path/of/your/file'
>>> backend.copy_if_symlink_fails(src, dst)
False
>>> src = 'petrel://path/of/dir'
>>> dst = 'petrel://path/of/your/dir'
>>> backend.copy_if_symlink_fails(src, dst)
False
copyfile(src, dst)[source]

Copy a file src to dst and return the destination file.

src and dst should have the same prefix. If dst specifies a directory, the file will be copied into dst using the base filename from src. If dst specifies a file that already exists, it will be replaced.

Parameters
  • src (str or Path) – A file to be copied.

  • dst (str or Path) – Copy file to dst.

Returns

The destination file.

Return type

str

Raises

SameFileError – If src and dst are the same file, a SameFileError will be raised.

Examples

>>> backend = PetrelBackend()
>>> # dst is a file
>>> src = 'petrel://path/of/file'
>>> dst = 'petrel://path/of/file1'
>>> backend.copyfile(src, dst)
'petrel://path/of/file1'
>>> # dst is a directory
>>> dst = 'petrel://path/of/dir'
>>> backend.copyfile(src, dst)
'petrel://path/of/dir/file'
copyfile_from_local(src, dst)[source]

Upload a local file src to dst and return the destination file.

Parameters
  • src (str or Path) – A local file to be copied.

  • dst (str or Path) – Copy file to dst.

  • backend_args (dict, optional) – Arguments to instantiate the prefix of uri corresponding backend. Defaults to None.

Returns

If dst specifies a directory, the file will be copied into dst using the base filename from src.

Return type

str

Examples

>>> backend = PetrelBackend()
>>> # dst is a file
>>> src = 'path/of/your/file'
>>> dst = 'petrel://path/of/file1'
>>> backend.copyfile_from_local(src, dst)
'petrel://path/of/file1'
>>> # dst is a directory
>>> dst = 'petrel://path/of/dir'
>>> backend.copyfile_from_local(src, dst)
'petrel://path/of/dir/file'
copyfile_to_local(src, dst)[source]

Copy the file src to local dst and return the destination file.

If dst specifies a directory, the file will be copied into dst using the base filename from src. If dst specifies a file that already exists, it will be replaced.

Parameters
  • src (str or Path) – A file to be copied.

  • dst (str or Path) – Copy file to to local dst.

Returns

If dst specifies a directory, the file will be copied into dst using the base filename from src.

Return type

str

Examples

>>> backend = PetrelBackend()
>>> # dst is a file
>>> src = 'petrel://path/of/file'
>>> dst = 'path/of/your/file'
>>> backend.copyfile_to_local(src, dst)
'path/of/your/file'
>>> # dst is a directory
>>> dst = 'path/of/your/dir'
>>> backend.copyfile_to_local(src, dst)
'path/of/your/dir/file'
copytree(src, dst)[source]

Recursively copy an entire directory tree rooted at src to a directory named dst and return the destination directory.

src and dst should have the same prefix.

Parameters
  • src (str or Path) – A directory to be copied.

  • dst (str or Path) – Copy directory to dst.

  • backend_args (dict, optional) – Arguments to instantiate the prefix of uri corresponding backend. Defaults to None.

Returns

The destination directory.

Return type

str

Raises

FileExistsError – If dst had already existed, a FileExistsError will be raised.

Examples

>>> backend = PetrelBackend()
>>> src = 'petrel://path/of/dir'
>>> dst = 'petrel://path/of/dir1'
>>> backend.copytree(src, dst)
'petrel://path/of/dir1'
copytree_from_local(src, dst)[source]

Recursively copy an entire directory tree rooted at src to a directory named dst and return the destination directory.

Parameters
  • src (str or Path) – A local directory to be copied.

  • dst (str or Path) – Copy directory to dst.

Returns

The destination directory.

Return type

str

Raises

FileExistsError – If dst had already existed, a FileExistsError will be raised.

Examples

>>> backend = PetrelBackend()
>>> src = 'path/of/your/dir'
>>> dst = 'petrel://path/of/dir1'
>>> backend.copytree_from_local(src, dst)
'petrel://path/of/dir1'
copytree_to_local(src, dst)[source]

Recursively copy an entire directory tree rooted at src to a local directory named dst and return the destination directory.

Parameters
  • src (str or Path) – A directory to be copied.

  • dst (str or Path) – Copy directory to local dst.

  • backend_args (dict, optional) – Arguments to instantiate the prefix of uri corresponding backend. Defaults to None.

Returns

The destination directory.

Return type

str

Examples

>>> backend = PetrelBackend()
>>> src = 'petrel://path/of/dir'
>>> dst = 'path/of/your/dir'
>>> backend.copytree_to_local(src, dst)
'path/of/your/dir'
exists(filepath)[source]

Check whether a file path exists.

Parameters

filepath (str or Path) – Path to be checked whether exists.

Returns

Return True if filepath exists, False otherwise.

Return type

bool

Examples

>>> backend = PetrelBackend()
>>> filepath = 'petrel://path/of/file'
>>> backend.exists(filepath)
True
generate_presigned_url(url, client_method='get_object', expires_in=3600)[source]

Generate the presigned url of video stream which can be passed to mmcv.VideoReader. Now only work on Petrel backend.

Note

Now only work on Petrel backend.

Parameters
  • url (str) – Url of video stream.

  • client_method (str) – Method of client, ‘get_object’ or ‘put_object’. Default: ‘get_object’.

  • expires_in (int) – expires, in seconds. Default: 3600.

Returns

Generated presigned url.

Return type

str

get(filepath)[source]

Read bytes from a given filepath with ‘rb’ mode.

Parameters

filepath (str or Path) – Path to read data.

Returns

Return bytes read from filepath.

Return type

bytes

Examples

>>> backend = PetrelBackend()
>>> filepath = 'petrel://path/of/file'
>>> backend.get(filepath)
b'hello world'
get_local_path(filepath)[source]

Download a file from filepath to a local temporary directory, and return the temporary path.

get_local_path is decorated by contxtlib.contextmanager(). It can be called with with statement, and when exists from the with statement, the temporary path will be released.

Parameters

filepath (str or Path) – Download a file from filepath.

Yields

Iterable[str] – Only yield one temporary path.

Return type

Generator[Union[str, pathlib.Path], None, None]

Examples

>>> backend = PetrelBackend()
>>> # After existing from the ``with`` clause,
>>> # the path will be removed
>>> filepath = 'petrel://path/of/file'
>>> with backend.get_local_path(filepath) as path:
...     # do something here
get_text(filepath, encoding='utf-8')[source]

Read text from a given filepath with ‘r’ mode.

Parameters
  • filepath (str or Path) – Path to read data.

  • encoding (str) – The encoding format used to open the filepath. Defaults to ‘utf-8’.

Returns

Expected text reading from filepath.

Return type

str

Examples

>>> backend = PetrelBackend()
>>> filepath = 'petrel://path/of/file'
>>> backend.get_text(filepath)
'hello world'
isdir(filepath)[source]

Check whether a file path is a directory.

Parameters

filepath (str or Path) – Path to be checked whether it is a directory.

Returns

Return True if filepath points to a directory, False otherwise.

Return type

bool

Examples

>>> backend = PetrelBackend()
>>> filepath = 'petrel://path/of/dir'
>>> backend.isdir(filepath)
True
isfile(filepath)[source]

Check whether a file path is a file.

Parameters

filepath (str or Path) – Path to be checked whether it is a file.

Returns

Return True if filepath points to a file, False otherwise.

Return type

bool

Examples

>>> backend = PetrelBackend()
>>> filepath = 'petrel://path/of/file'
>>> backend.isfile(filepath)
True
join_path(filepath, *filepaths)[source]

Concatenate all file paths.

Join one or more filepath components intelligently. The return value is the concatenation of filepath and any members of *filepaths.

Parameters
Returns

The result after concatenation.

Return type

str

Examples

>>> backend = PetrelBackend()
>>> filepath = 'petrel://path/of/file'
>>> backend.join_path(filepath, 'another/path')
'petrel://path/of/file/another/path'
>>> backend.join_path(filepath, '/another/path')
'petrel://path/of/file/another/path'
list_dir_or_file(dir_path, list_dir=True, list_file=True, suffix=None, recursive=False)[source]

Scan a directory to find the interested directories or files in arbitrary order.

Note

Petrel has no concept of directories but it simulates the directory hierarchy in the filesystem through public prefixes. In addition, if the returned path ends with ‘/’, it means the path is a public prefix which is a logical directory.

Note

list_dir_or_file() returns the path relative to dir_path. In addition, the returned path of directory will not contains the suffix ‘/’ which is consistent with other backends.

Parameters
  • dir_path (str | Path) – Path of the directory.

  • list_dir (bool) – List the directories. Defaults to True.

  • list_file (bool) – List the path of files. Defaults to True.

  • suffix (str or tuple[str], optional) – File suffix that we are interested in. Defaults to None.

  • recursive (bool) – If set to True, recursively scan the directory. Defaults to False.

Yields

Iterable[str] – A relative path to dir_path.

Return type

Iterator[str]

Examples

>>> backend = PetrelBackend()
>>> dir_path = 'petrel://path/of/dir'
>>> # list those files and directories in current directory
>>> for file_path in backend.list_dir_or_file(dir_path):
...     print(file_path)
>>> # only list files
>>> for file_path in backend.list_dir_or_file(dir_path, list_dir=False):
...     print(file_path)
>>> # only list directories
>>> for file_path in backend.list_dir_or_file(dir_path, list_file=False):
...     print(file_path)
>>> # only list files ending with specified suffixes
>>> for file_path in backend.list_dir_or_file(dir_path, suffix='.txt'):
...     print(file_path)
>>> # list all files and directory recursively
>>> for file_path in backend.list_dir_or_file(dir_path, recursive=True):
...     print(file_path)
put(obj, filepath)[source]

Write bytes to a given filepath.

Parameters
  • obj (bytes) – Data to be saved.

  • filepath (str or Path) – Path to write data.

Return type

None

Examples

>>> backend = PetrelBackend()
>>> filepath = 'petrel://path/of/file'
>>> backend.put(b'hello world', filepath)
put_text(obj, filepath, encoding='utf-8')[source]

Write text to a given filepath.

Parameters
  • obj (str) – Data to be written.

  • filepath (str or Path) – Path to write data.

  • encoding (str) – The encoding format used to encode the obj. Defaults to ‘utf-8’.

Return type

None

Examples

>>> backend = PetrelBackend()
>>> filepath = 'petrel://path/of/file'
>>> backend.put_text('hello world', filepath)
remove(filepath)[source]

Remove a file.

Parameters

filepath (str or Path) – Path to be removed.

Raises
  • FileNotFoundError – If filepath does not exist, an FileNotFoundError will be raised.

  • IsADirectoryError – If filepath is a directory, an IsADirectoryError will be raised.

Return type

None

Examples

>>> backend = PetrelBackend()
>>> filepath = 'petrel://path/of/file'
>>> backend.remove(filepath)
rmtree(dir_path)[source]

Recursively delete a directory tree.

Parameters

dir_path (str or Path) – A directory to be removed.

Return type

None

Examples

>>> backend = PetrelBackend()
>>> dir_path = 'petrel://path/of/dir'
>>> backend.rmtree(dir_path)
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