ButlerURI¶

class lsst.daf.butler.ButlerURI¶

Bases: object

Convenience wrapper around URI parsers.

Provides access to URI components and can convert file paths into absolute path URIs. Scheme-less URIs are treated as if they are local file system paths and are converted to absolute URIs.

A specialist subclass is created for each supported URI scheme.

Parameters:

uri : str or urllib.parse.ParseResult: URI in string form. Can be scheme-less if referring to a local filesystem path.
root : str, optional: When fixing up a relative path in a file scheme or if scheme-less, use this as the root. Must be absolute. If None the current working directory will be used.
forceAbsolute : bool, optional: If True, scheme-less relative URI will be converted to an absolute path using a file scheme. If False scheme-less URI will remain scheme-less and will not be updated to file or absolute path.
forceDirectory: `bool`, optional: If True forces the URI to end with a separator, otherwise given URI is interpreted as is.

Attributes Summary

`fragment`	The fragment component of the URI.
`netloc`	The URI network location.
`ospath`	Path component of the URI localized to current OS.
`params`	Any parameters included in the URI.
`path`	The path component of the URI.
`query`	Any query strings included in the URI.
`quotePaths`	True if path-like elements modifying a URI should be quoted.
`relativeToPathRoot`	Returns path relative to network location.
`scheme`	The URI scheme (`://` is not part of the scheme).
`transferDefault`	Default mode to use for transferring if `auto` is specified.
`transferModes`	Transfer modes supported by this implementation.
`unquoted_path`	The path component of the URI with any URI quoting reversed.

Methods Summary

`as_local`()	Return the location of the (possibly remote) resource in the local file system.
`basename`()	Returns the base name, last element of path, of the URI.
`dirname`()	Returns a ButlerURI containing all the directories of the path attribute.
`exists`()	Indicate that the resource is available.
`getExtension`()	Return the file extension(s) associated with this URI path.
`geturl`()	Return the URI in string form.
`isabs`()	Indicate that the resource is fully specified.
`join`(path)	Create a new `ButlerURI` with additional path components including a file.
`mkdir`()	For a dir-like URI, create the directory resource if it does not already exist.
`read`(size)	Open the resource and return the contents in bytes.
`relative_to`(other)	Return the relative path from this URI to the other URI.
`remove`()	Remove the resource.
`replace`(**kwargs)	Replace components in a URI with new values and return a new instance.
`split`()	Splits URI into head and tail.
`transfer_from`(src, transfer, overwrite, …)	Transfer the current resource to a new location.
`updateFile`(newfile)	Update in place the final component of the path with the supplied file name.
`write`(data, overwrite)	Write the supplied bytes to the new resource.

Attributes Documentation

fragment¶: The fragment component of the URI.

netloc¶: The URI network location.

ospath¶: Path component of the URI localized to current OS.

params¶: Any parameters included in the URI.

path¶: The path component of the URI.

query¶: Any query strings included in the URI.

quotePaths = True¶

True if path-like elements modifying a URI should be quoted.

All non-schemeless URIs have to internally use quoted paths. Therefore if a new file name is given (e.g. to updateFile or join) a decision must be made whether to quote it to be consistent.

relativeToPathRoot¶

Returns path relative to network location.

Effectively, this is the path property with posix separator stripped from the left hand side of the path.

Always unquotes.

scheme¶: The URI scheme (:// is not part of the scheme).

transferDefault = 'copy'¶: Default mode to use for transferring if auto is specified.

transferModes = ('copy', 'auto', 'move')¶

Transfer modes supported by this implementation.

Move is special in that it is generally a copy followed by an unlink. Whether that unlink works depends critically on whether the source URI implements unlink. If it does not the move will be reported as a failure.

unquoted_path¶: The path component of the URI with any URI quoting reversed.

Methods Documentation

as_local() → Tuple[str, bool]¶

Return the location of the (possibly remote) resource in the local file system.

Returns:	path : `str` If this is a remote resource, it will be a copy of the resource on the local file system, probably in a temporary directory. For a local resource this should be the actual path to the resource. is_temporary : `bool` Indicates if the local path is a temporary file or not.

basename() → str¶

Returns the base name, last element of path, of the URI. If URI ends on a slash returns an empty string. This is the second element returned by split().

Equivalent of os.path.basename().

Returns:	tail : `str` Last part of the path attribute. Trail will be empty if path ends on a separator.

dirname() → lsst.daf.butler.core._butlerUri.ButlerURI¶

Returns a ButlerURI containing all the directories of the path attribute.

Equivalent of os.path.dirname()

Returns:	head : `ButlerURI` Everything except the tail of path attribute, expanded and normalized as per ButlerURI rules.

exists() → bool¶

Indicate that the resource is available.

Returns:	exists : `bool` `True` if the resource exists.

getExtension() → str¶

Return the file extension(s) associated with this URI path.

Returns:	ext : `str` The file extension (including the `.`). Can be empty string if there is no file extension. Will return all file extensions as a single extension such that `file.fits.gz` will return a value of `.fits.gz`.

geturl() → str¶

Return the URI in string form.

Returns:	url : `str` String form of URI.

isabs() → bool¶

Indicate that the resource is fully specified.

For non-schemeless URIs this is always true.

Returns:	isabs : `bool` `True` in all cases except schemeless URI.

join(path: str) → lsst.daf.butler.core._butlerUri.ButlerURI¶

Create a new ButlerURI with additional path components including a file.

Parameters:	path : `str` Additional file components to append to the current URI. Assumed to include a file at the end. Will be quoted depending on the associated URI scheme.
Returns:	new : `ButlerURI` New URI with any file at the end replaced with the new path components.

Notes

Schemeless URIs assume local path separator but all other URIs assume POSIX separator if the supplied path has directory structure. It may be this never becomes a problem but datastore templates assume POSIX separator is being used.

mkdir() → None¶: For a dir-like URI, create the directory resource if it does not already exist.

read(size: int = -1) → bytes¶

Open the resource and return the contents in bytes.

Parameters:	size : `int`, optional The number of bytes to read. Negative or omitted indicates that all data should be read.

relative_to(other: lsst.daf.butler.core._butlerUri.ButlerURI) → Optional[str]¶

Return the relative path from this URI to the other URI.

Parameters:	other : `ButlerURI` URI to use to calculate the relative path. Must be a parent of this URI.
Returns:	subpath : `str` The sub path of this URI relative to the supplied other URI. Returns `None` if there is no parent child relationship. Scheme and netloc must match.

remove() → None¶: Remove the resource.

replace(**kwargs) → lsst.daf.butler.core._butlerUri.ButlerURI¶

Replace components in a URI with new values and return a new instance.

Returns:	new : `ButlerURI` New `ButlerURI` object with updated values.

split() → Tuple[lsst.daf.butler.core._butlerUri.ButlerURI, str]¶

Splits URI into head and tail. Equivalent to os.path.split where head preserves the URI components.

Returns:	head: `ButlerURI` Everything leading up to tail, expanded and normalized as per ButlerURI rules. tail : `str` Last `self.path` component. Tail will be empty if path ends on a separator. Tail will never contain separators. It will be unquoted.

transfer_from(src: ButlerURI, transfer: str, overwrite: bool = False, transaction: Optional[Union[DatastoreTransaction, NoTransaction]] = None) → None¶

Transfer the current resource to a new location.

Parameters:

src : ButlerURI: Source URI.
transfer : str: Mode to use for transferring the resource. Generically there are many standard options: copy, link, symlink, hardlink, relsymlink. Not all URIs support all modes.
overwrite : bool, optional: Allow an existing file to be overwritten. Defaults to False.
transaction : DatastoreTransaction, optional: A transaction object that can (depending on implementation) rollback transfers on error. Not guaranteed to be implemented.

Notes

Conceptually this is hard to scale as the number of URI schemes grow. The destination URI is more important than the source URI since that is where all the transfer modes are relevant (with the complication that “move” deletes the source).

Local file to local file is the fundamental use case but every other scheme has to support “copy” to local file (with implicit support for “move”) and copy from local file. All the “link” options tend to be specific to local file systems.

“move” is a “copy” where the remote resource is deleted at the end. Whether this works depends on the source URI rather than the destination URI. Reverting a move on transaction rollback is expected to be problematic if a remote resource was involved.

updateFile(newfile: str) → None¶

Update in place the final component of the path with the supplied file name.

Parameters:	newfile : `str` File name with no path component.

Notes

Updates the URI in place. Updates the ButlerURI.dirLike attribute. The new file path will be quoted if necessary.

write(data: bytes, overwrite: bool = True) → None¶

Write the supplied bytes to the new resource.

Parameters:	data : `bytes` The bytes to write to the resource. The entire contents of the resource will be replaced. overwrite : `bool`, optional If `True` the resource will be overwritten if it exists. Otherwise the write will fail.

Navigation

ButlerURI¶