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 or ButlerURI, 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. Can be a file URI.

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.

isTemporary : bool, optional

If True indicates that this URI points to a temporary resource.

Attributes Summary

fragment The fragment component of the URI.
isLocal If True this URI refers to a local file.
is_root True if this URI points to the root of the network location.
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.
parent() Returns a ButlerURI containing all the directories of the path attribute, minus the last one.
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.
size() For non-dir-like URI, return the size of the resource.
split() Splits URI into head and tail.
transfer_from(src, transfer, overwrite, …) Transfer the current resource to a new location.
updateExtension(ext) Update the file extension associated with this ButlerURI in place.
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.

isLocal = False

If True this URI refers to a local file.

is_root

True if this URI points to the root of the network location.

This means that the path components refers to the top level.

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() → Iterator[lsst.daf.butler.core._butlerUri._butlerUri.ButlerURI]

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

Yields:
local : ButlerURI

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.

Notes

The context manager will automatically delete any local temporary file.

Examples

Should be used as a context manager:

with uri.as_local() as local:
    ospath = local.ospath
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.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. Usually returns only the last file extension unless there is a special extension modifier indicating file compression, in which case the combined extension (e.g. .fits.gz) will be returned.

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: Union[str, lsst.daf.butler.core._butlerUri._butlerUri.ButlerURI]) → lsst.daf.butler.core._butlerUri._butlerUri.ButlerURI

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

Parameters:
path : str, ButlerURI

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. If the path looks like a URI with a scheme referring to an absolute location, it will be returned directly (matching the behavior of os.path.join()). It can also be a ButlerURI.

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.

parent() → lsst.daf.butler.core._butlerUri._butlerUri.ButlerURI

Returns a ButlerURI containing all the directories of the path attribute, minus the last one.

Returns:
head : ButlerURI

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

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.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.ButlerURI

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

Returns:
new : ButlerURI

New ButlerURI object with updated values.

size() → int

For non-dir-like URI, return the size of the resource.

Returns:
sz : int

The size in bytes of the resource associated with this URI. Returns 0 if dir-like.

split() → Tuple[lsst.daf.butler.core._butlerUri._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.

updateExtension(ext: Optional[str]) → None

Update the file extension associated with this ButlerURI in place.

All file extensions are replaced.

Parameters:
ext : str or None

New extension. If an empty string is given any extension will be removed. If None is given there will be no change.

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.