Package: cs.fileutils
My grab bag of convenience functions for files and filenames/pathnames.Latest release 20240201:makelockfile: new optional keepopen parameter - if true return the lock path and an open file descriptor.lockfile(): keep the lock file open to aid debugging with eg lsof.Functionabspath_from_file(path, from_file)Return the absolute path ofpathwith respect tofrom_file,
as one might do for an include file.Functionatomic_filename(filename, exists_ok=False, placeholder=False, dir=None, prefix=None, suffix=None, rename_func=<built-in function rename>, **kw)A context manager to createfilenameatomicly on completion.
This returns aNamedTemporaryFileto use to create the file contents.
On completion the temporary file is renamed to the target namefilename.Parameters:filename: the file name to createexists_ok: defaultFalse;
if true it not an error iffilenamealready existsplaceholder: create a placeholder file atfilenamewhile the real contents are written to the temporary filedir: passed toNamedTemporaryFile, specifies the directory
to hold the temporary file; the default isdirname(filename)to ensure the rename is atomicprefix: passed toNamedTemporaryFile, specifies a prefix
for the temporary file; the default is a dot ('.') plus the prefix
fromsplitext(basename(filename))suffix: passed toNamedTemporaryFile, specifies a suffix
for the temporary file; the default is the extension obtained
fromsplitext(basename(filename))rename_func: a callable accepting(tempname,filename)used to rename the temporary file to the final name; the
default isos.renameand this parametr exists to accept
something such asFSTags.moveOther keyword arguments are passed to theNamedTemporaryFileconstructor.Example:>>> import os
>>> from os.path import exists as existspath
>>> fn = 'test_atomic_filename'
>>> with atomic_filename(fn, mode='w') as f:
...     assert not existspath(fn)
...     print('foo', file=f)
...     assert not existspath(fn)
...
>>> assert existspath(fn)
>>> assert open(fn).read() == 'foo\n'
>>> os.remove(fn)ClassBackedFile(ReadMixin)A RawIOBase duck type
which uses a backing file for initial data
and writes new data to a front scratch file.MethodBackedFile.__init__(self, back_file, dirpath=None):
Initialise the BackedFile usingback_filefor the backing data.ClassBackedFile_TestMethodsMixin for testing subclasses of BackedFile.
Tests self.backed_fp.Functionbyteses_as_fd(bss, **kw)Deliver the iterable of bytesbssas a readable file descriptor.
Return the file descriptor.
Any keyword arguments are passed toCornuCopyBuffer.as_fd.Example:

       # present a passphrase for use as in input file descrptor
       # for a subprocess
       rfd = byteses_as_fd([(passphrase + '').encode()])Functioncommon_path_prefix(*paths)Return the common path prefix of thepaths.Note that the common prefix of'/a/b/c1'and'/a/b/c2'is'/a/b/',not'/a/b/c'.Callers may find it useful to preadjust the supplied paths
withnormpath,abspathorrealpathfromos.path;
see theos.pathdocumentation for the various caveats
which go with those functions.Examples:>>> # the obvious
>>> common_path_prefix('', '')
''
>>> common_path_prefix('/', '/')
'/'
>>> common_path_prefix('a', 'a')
'a'
>>> common_path_prefix('a', 'b')
''
>>> # nonempty directory path prefixes end in os.sep
>>> common_path_prefix('/', '/a')
'/'
>>> # identical paths include the final basename
>>> common_path_prefix('p/a', 'p/a')
'p/a'
>>> # the comparison does not normalise paths
>>> common_path_prefix('p//a', 'p//a')
'p//a'
>>> common_path_prefix('p//a', 'p//b')
'p//'
>>> common_path_prefix('p//a', 'p/a')
'p/'
>>> common_path_prefix('p/a', 'p/b')
'p/'
>>> # the comparison strips complete unequal path components
>>> common_path_prefix('p/a1', 'p/a2')
'p/'
>>> common_path_prefix('p/a/b1', 'p/a/b2')
'p/a/'
>>> # contrast with cs.lex.common_prefix
>>> common_prefix('abc/def', 'abc/def1')
'abc/def'
>>> common_path_prefix('abc/def', 'abc/def1')
'abc/'
>>> common_prefix('abc/def', 'abc/def1', 'abc/def2')
'abc/def'
>>> common_path_prefix('abc/def', 'abc/def1', 'abc/def2')
'abc/'Functioncompare(f1, f2, mode='rb')Compare the contents of two file-like objectsf1andf2for equality.Iff1orf2is a string, open the named file usingmode(default:"rb").Functioncopy_data(fpin, fpout, nbytes, rsize=None)Copynbytesof data fromfpintofpout,
return the number of bytes copied.Parameters:nbytes: number of bytes to copy.
IfNone, copy until EOF.rsize: read size, defaultDEFAULT_READSIZE.Functioncrop_name(name, ext=None, name_max=255)Crop a file basename so as not to exceedname_maxin length.
Return the originalnameif it already short enough.
Otherwise cropnamebefore the file extension
to make it short enough.Parameters:name: the file basename to cropext: optional file extension;
the default is to infer the extension withos.path.splitext.name_max: optional maximum length, default:255Functiondatafrom(f, offset=None, readsize=None, maxlength=None)General purpose reader for files yielding data fromoffset.WARNING: this function might move the file pointer.Parameters:f: the file from which to read data;
if a string, the file is opened with mode="rb";
if an int, treated as an OS file descriptor;
otherwise presumed to be a file-like object.
If that object has a.fileno()method, treat that as an
OS file descriptor and use it.offset: starting offset for the datamaxlength: optional maximum amount of data to yieldreadsize: read size, default DEFAULT_READSIZE.For file-like objects, the read1 method is used in preference
to read if available. The file pointer is briefly moved during
fetches.Functiondatafrom_fd(fd, offset=None, readsize=None, aligned=True, maxlength=None)General purpose reader for file descriptors yielding data fromoffset.Note: This does not move the file descriptor positionifthe file is seekable.Parameters:fd: the file descriptor from which to read.offset: the offset from which to read.
If omitted, use the current file descriptor position.readsize: the read size, default:DEFAULT_READSIZEaligned: if true (the default), the first read is sized
to align the new offset with a multiple ofreadsize.maxlength: if specified yield no more than this many bytes of data.Functionfile_based(*da, **dkw)A decorator which caches a value obtained from a file.In addition to all the keyword arguments for@cs.deco.cachedmethod,
this decorator also accepts the following arguments:attr_name: the name for the associated attribute, used as
the basis for the internal cache value attributefilename: the filename to monitor.
Default from the._{attr_name}__filenameattribute.
This value will be passed to the method as thefilenamekeyword
parameter.poll_delay: delay between file polls, defaultDEFAULT_POLL_INTERVAL.sig_func: signature function used to encapsulate the relevant
information about the file; default
cs.filestate.FileState({filename}).If the decorated function raises OSError with errno == ENOENT,
this returns None. Other exceptions are reraised.Functionfile_data(fp, nbytes=None, rsize=None)Readnbytesof data fromfpand yield the chunks as read.Parameters:nbytes: number of bytes to read; if None read until EOF.rsize: read size, default DEFAULT_READSIZE.Functionfile_property(*da, **dkw)A property whose value reloads if a file changes.Functionfiles_property(func)A property whose value reloads if any of a list of files changes.Note: this is just the default mode formake_files_property.funcaccepts the file path and returns the new value.
The underlying attribute name is'_'+func.__name__,
the default frommake_files_property().
The attribute{attr_name}_lockis a mutex controlling access to the property.
The attributes{attr_name}_filestatesand{attr_name}_pathstrack the
associated file states.
The attribute{attr_name}_lastpolltracks the last poll time.The decorated function is passed the current list of files
and returns the new list of files and the associated value.One example use would be a configuration file with recurive
include operations; the inner function would parse the first
file in the list, and the parse would accumulate this filename
and those of any included files so that they can be monitored,
triggering a fresh parse if one changes.Example:class C(object):
  def __init__(self):
    self._foo_path = '.foorc'
  @files_property
  def foo(self,paths):
    new_paths, result = parse(paths[0])
    return new_paths, resultThe load function is called on the first access and on every
access thereafter where an associated file'sFileStatehas
changed and the time since the last successful load exceeds
the poll_rate (1s). An attempt at avoiding races is made by
ignoring reloads that raise exceptions and ignoring reloads
where files that were stat()ed during the change check have
changed state after the load.Functionfind(path, select=None, sort_names=True)Walk a directory treepathyielding selected paths.Note: not selecting a directory prunes all its descendants.Functionfindup(path, test, first=False)Test the pathnameabspath(path)and each of its ancestors
against the callabletest,
yielding paths satisfying the test.Iffirstis true (defaultFalse)
this function always yields exactly one value,
either the first path satisfying the test orNone.
This mode supports a use such as:matched_path = next(findup(path, test, first=True))
# post condition: matched_path will be `None` on no match
# otherwise the first matching pathFunctiongzifopen(path, mode='r', *a, **kw)Context manager to open a file which may be a plain file or a gzipped file.Ifpathends with'.gz'then the filesystem paths attempted
arepathandpathwithout the extension, otherwise the
filesystem paths attempted arepath+'.gz'andpath.  In
this way a path ending in'.gz'indicates a preference for
a gzipped file otherwise an uncompressed file.However, if exactly one of the paths exists already then only
that path will be used.Note that the single character modes'r','a','w'and'x'are text mode for both uncompressed and gzipped opens,
like the builtinopenandunlikegzip.open.
This is to ensure equivalent behaviour.Functioniter_fd(fd, **kw)Iterate over data from the file descriptorfd.Functioniter_file(f, **kw)Iterate over data from the filef.Functionlines_of(fp, partials=None)Generator yielding lines from a file until EOF.
Intended for file-like objects that lack a line iteration API.Functionlockfile(path, *, ext=None, poll_interval=None, timeout=None, runstate: cs.resources.RunState)A context manager which takes and holds a lock file.
An open file descriptor is kept for the lock file as well
to aid locating the process holding the lock file using eglsof.Parameters:path: the base associated with the lock file.ext: the extension to the base used to construct the lock file name.
Default:'.lock'timeout: maximum time to wait before failing.
Default:None(wait forever).poll_interval: polling frequency when timeout is not0.runstate: optionalRunStateduck instance supporting cancellation.Functionmake_files_property(attr_name=None, unset_object=None, poll_rate=1.0)Construct a decorator that watches multiple associated files.Parameters:attr_name: the underlying attribute, default:'_'+func.__name__unset_object: the sentinel value for "uninitialised", default:Nonepoll_rate: how often in seconds to poll the file for changes,
default fromDEFAULT_POLL_INTERVAL:1.0The attributeattr_name_lockcontrols access to the property.
The attributesattr_name_filestatesandattr_name_pathstrack the
associated files' state.
The attributeattr_name_lastpolltracks the last poll time.The decorated function is passed the current list of files
and returns the new list of files and the associated value.One example use would be a configuration file with recursive
include operations; the inner function would parse the first
file in the list, and the parse would accumulate this filename
and those of any included files so that they can be monitored,
triggering a fresh parse if one changes.Example:class C(object):
  def __init__(self):
    self._foo_path = '.foorc'
  @files_property
  def foo(self,paths):
    new_paths, result = parse(paths[0])
    return new_paths, resultThe load function is called on the first access and on every
access thereafter where an associated file'sFileStatehas
changed and the time since the last successful load exceeds
thepoll_rate.An attempt at avoiding races is made by
ignoring reloads that raise exceptions and ignoring reloads
where files that wereos.stat()ed during the change check have
changed state after the load.Functionmakelockfile(path, *, ext=None, poll_interval=None, timeout=None, runstate: cs.resources.RunState, keepopen=False)Create a lockfile and return its path.The lockfile can be removed withos.remove.
This is the core functionality supporting thelockfile()context manager.Parameters:path: the base associated with the lock file,
often the filesystem object whose access is being managed.ext: the extension to the base used to construct the lockfile name.
Default: ".lock"timeout: maximum time to wait before failing.
Default:None(wait forever).
Note that zero is an accepted value
and requires the lock to succeed on the first attempt.poll_interval: polling frequency when timeout is not 0.runstate: optionalRunStateduck instance supporting cancellation.
Note that if a cancelledRunStateis provided
no attempt will be made to make the lockfile.keepopen: optional flag, defaultFalse:
if true, do not close the lockfile and return(lockpath,lockfd)being the lock file path and the open file descriptorFunctionmax_suffix(dirpath, prefix)Compute the highest existing numeric suffix
for names starting withprefix.This is generally used as a starting point for picking
a new numeric suffix.Functionmkdirn(path, sep='')Create a new directory namedpath+sep+n,
wherenexceeds any name already present.Parameters:path: the basic directory path.sep: a separator betweenpathandn.
Default:''FunctionNamedTemporaryCopy(f, progress=False, progress_label=None, **kw)A context manager yielding a temporary copy offilenameas returned byNamedTemporaryFile(**kw).Parameters:f: the name of the file to copy, or an open binary file,
or aCornuCopyBufferprogress: an optional progress indicator, defaultFalse;
if abool, show a progress bar for the copy phase if true;
if anint, show a progress bar for the copy phase
if the file size equals or exceeds the value;
otherwise it should be acs.progress.Progressinstanceprogress_label: option progress bar label,
only used if a progress bar is made
Other keyword parameters are passed totempfile.NamedTemporaryFile.ClassNullFileWritable file that discards its input.Note that this isnotan open ofos.devnull;
it just discards writes and is not the underlying file descriptor.MethodNullFile.__init__(self):
Initialise the file offset to 0.ClassPathname(builtins.str)Subclass of str presenting convenience properties useful for
format strings related to file paths.Functionpoll_file(path, old_state, reload_file, missing_ok=False)Watch a file for modification by polling its state as obtained
byFileState().
Callreload_file(path)if the state changes.
Return(new_state,reload_file(path))if the file was modified
and was unchanged (stable state) before and after the reload_file().
Otherwise return(None,None).This may raise anOSErrorif thepathcannot beos.stat()ed
and of course for any exceptions that occur callingreload_file.Ifmissing_okis true then a failure toos.stat()which
raisesOSErrorwithENOENTwill just return(None,None).Functionread_data(fp, nbytes, rsize=None)Readnbytesof data fromfp, return the data.Parameters:nbytes: number of bytes to copy.
IfNone, copy until EOF.rsize: read size, defaultDEFAULT_READSIZE.Functionread_from(fp, rsize=None, tail_mode=False, tail_delay=None)Generator to present text or data from an open file until EOF.Parameters:rsize: read size, default: DEFAULT_READSIZEtail_mode: if true, yield an empty chunk at EOF, allowing resumption
if the file grows.ClassReadMixinUseful read methods to accomodate modes not necessarily available in a class.Note that this mixin presumes that the attributeself._lockis a threading.RLock like context manager.Classes using this mixin should consider overriding the default
.datafrom method with something more efficient or direct.Functionrewrite(filepath, srcf, mode='w', backup_ext=None, do_rename=False, do_diff=None, empty_ok=False, overwrite_anyway=False)Rewrite the filefilepathwith data from the file objectsrcf.Parameters:filepath: the name of the file to rewrite.srcf: the source file containing the new content.mode: the write-mode for the file, default'w'(for text);
use'wb'for binary data.empty_ok: if true (defaultFalse),
do not raiseValueErrorif the new data are empty.overwrite_anyway: if true (defaultFalse),
skip the content check and overwrite unconditionally.backup_ext: if a nonempty string,
take a backup of the original atfilepath + backup_ext.do_diff: if notNone, calldo_diff(filepath,tempfile).do_rename: if true (defaultFalse),
rename the temp file tofilepathafter copying the permission bits.
Otherwise (default), copy the tempfile tofilepath;
this preserves the file's inode and permissions etc.Functionrewrite_cmgr(filepath, mode='w', **kw)Rewrite a file, presented as a context manager.Parameters:mode: file write mode, defaulting to "w" for text.Other keyword parameters are passed torewrite().Example:with rewrite_cmgr(pathname, do_rename=True) as f:
    ... write new content to f ...ClassRWFileBlockCacheA scratch file for storing data.MethodRWFileBlockCache.__init__(self, pathname=None, dirpath=None, suffix=None, lock=None):
Initialise the file.Parameters:pathname: path of file. If None, create a new file with
tempfile.mkstemp using dir=dirpathand unlink that file once
opened.dirpath: location for the file if made by mkstemp as above.lock: an object to use as a mutex, allowing sharing with
some outer system. A Lock will be allocated if omitted.Functionsaferename(oldpath, newpath)Rename a path usingos.rename(),
but raise an exception if the target path already exists.
Note: slightly racey.Functionseekable(fp)Try to test whether a filelike object is seekable.First try theIOBase.seekablemethod, otherwise try getting a file
descriptor fromfp.filenoandos.stat()ing that,
otherwise returnFalse.ClassTeeAn object with .write, .flush and .close methods
which copies data to multiple output files.MethodTee.__init__(self, *fps):
Initialise the Tee; any arguments are taken to be output file objects.Functiontee(fp, fp2)Context manager duplicating .write and .flush from fp to fp2.Functiontmpdir()Return the pathname of the default temporary directory for scratch data,
the environment variable$TMPDIRor'/tmp'.Functiontmpdirn(tmp=None)Make a new temporary directory with a numeric suffix.Functiontrysaferename(oldpath, newpath)Asaferename()that returnsTrueon success,Falseon failure.Release LogRelease 20240201:makelockfile: new optional keepopen parameter - if true return the lock path and an open file descriptor.lockfile(): keep the lock file open to aid debugging with eg lsof.Release 20231129:atomic_filename: accept optional rename_func to use instead of os.rename, supports using FSTags.move.atomic_filename: clean up the temp file.Release 20230421:
atomic_filename: raise FileExistsError instead of ValueError if not exists_ok and existspath(filename).Release 20230401:
Replaced a lot of runstate plumbing with @uses_runstate.Release 20221118:
atomic_filename: use shutil.copystat instead of shutil.copymode, bugfix the associated logic.Release 20220429:
Move longpath and shortpath to cs.fs, leave legacy names behind.Release 20211208:Move NDJSON stuff to separate cs.ndjson module.New gzifopen() function to open either a gzipped file or an uncompressed file.Release 20210906:
Additional release because I'm unsure @atomic_filename made it into the previous release.Release 20210731:
New atomic_filename context manager wrapping NamedTemporaryFile for presenting a file after its contents are prepared.Release 20210717:
Updates for recent cs.mappings-20210717 release.Release 20210420:Forensic prefix for NamedTemporaryCopy.UUIDNDJSONMapping: provide an empty .scan_errors on instantiation, avoids AttributeError if a scan never occurs.Release 20210306:datafrom_fd: fix use-before-set of is_seekable.RWFileBlockCache.put: remove assert(len(data)>0), adjust logic.Release 20210131:
crop_name: put ext before name_max, more likely to be specified, I think.Release 20201227.1:
Docstring tweak.Release 20201227:
scan_ndjson: optional errors_list to accrue errors during the scan.Release 20201108:
Bugfix rewrite_cmgr, failed to flush a file before copying its contents.Release 20201102:Newline delimited JSON (ndjson) support.New UUIDNDJSONMapping implementing a singleton cs.mappings.LoadableMappingMixin of cs.mappings.UUIDedDict subclass instances backed by an NDJSON file.New scan_ndjson() function to yield newline delimited JSON records.New write_ndjson() function to write newline delimited JSON records.New append_ndjson() function to append a single newline delimited JSON record to a file.New NamedTemporaryCopy for creating a temporary copy of a file with an optional progress bar.rewrite_cmgr: turn into a simple wrapper for rewrite.datafrom: make the offset parameter optional, tweak the @strable open function.datafrom_fd: support nonseekable file descriptors, document that for these the file position is moved (no pread support).New iter_fd and iter_file to return iterators of a file's data by utilising a CornuCopyBuffer.New byteses_as_fd to return a readable file descriptor receiving an iterable of bytes via a CornuCopyBuffer.Release 20200914:
New common_path_prefix to compare pathnames.Release 20200517:New crop_name() function to crop a file basename to fit within a specific length.New find() function complimenting findup (UNTESTED).Release 20200318:
New findup(path,test) generator to walk up a file tree.Release 20191006:
Adjust import of cs.deco.cachedmethod.Release 20190729:
datafrom_fd: makeoffsetoptional, defaulting to fd position at call.Release 20190617:
@file_based: adjust use of @cached from cached(wrap0, **dkw) to cached(**dkw)(wrap0).Release 20190101:
datafrom: add maxlength keyword arg, bugfix fd and f.fileno cases.Release 20181109:Various bugfixes for BackedFile.Use a file's .read1 method if available in some scenarios.makelockfile: accept am optional RunState control parameter, improve some behaviour.datafrom_fd: new optional maxlength parameter limiting the amount of data returned.datafrom_fd: by default, perform an initial read to align all subsequent reads with the readsize.drop fdreader, add datafrom(f, offset, readsize) accepting a file or a file descriptor, expose datafrom_fd.ReadMixin.datafrom now mandatory. Add ReadMixin.bufferfrom.Assorted other improvements, minor bugfixes, documentation improvements.Release 20171231.1:
Trite DISTINFO fix, no semantic changes.Release 20171231:
Update imports, bump DEFAULT_READSIZE from 8KiB to 128KiB.Release 20170608:Move lockfile and the SharedAppend* classes to cs.sharedfile.BackedFile internal changes.Release 20160918:BackedFile: redo implementation of .front_file to fix resource leak; add .len; add methods .spans, .front_spans and .back_spans to return information about front vs back data.seek: bugfix: seek should return the new file offset.BackedFile does not subclass RawIOBase, it just works like one.Release 20160828:Use "install_requires" instead of "requires" in DISTINFO.Rename maxFilenameSuffix to max_suffix.Pull in OpenSocket file-like socket wrapper from cs.venti.tcp.Update for cs.asynchron changes.... then move cs.fileutils.OpenSocket into new module cs.socketutils.New Tee class, for copying output to multiple files.NullFile class which discards writes (==> no-op for Tee).New class SavingFile to accrue output and move to specified pathname when complete.Memory usage improvements.Polyfill non-threadsafe implementation of pread if os.pread does not exist.New function seekable() to probe a file for seekability.SharedAppendFile: provide new .open(filemode) context manager for allowing direct file output for external users.New function makelockfile() presenting the logic to create a lock file separately from the lockfile context manager.Assorted bugfixes and improvements.Release 20150116:
Initial PyPI release.