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A nifty way to parse your file sequences.

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Overview

The seqparse module may be used to …

  • Scan specified paths for file sequences and “singletons,”

  • Construct frame and file sequence from supplied values, and

  • Query disk for overall footprint of tracked files.

The module also comes supplied with a simple tool named seqls that allows the user to scan multiple locations for file sequences and singletons from the command line.

If you’re curious about the regular expressions used to determine what is and isn’t a valid file sequence, take a look at the seqparse.regex module.

Frame Sequences

Frame sequences are broken down into comma-separated chunks of the format first frame - last frame x step where the following rules apply:

  • Frame numbers can be zero-padded,

  • Frame step (increment) is always a positive integer,

  • The number of digits in a frame may exceed the padding of a sequence, eg 001,010,100,1000,

  • Frame chunks with a specified step will always consist of three or more frames.

Examples of proper frame sequences:

  • Non-padded sequence, frames == (1, 3, 5, 7): 1-7x2

  • Four-padded sequence, frames == (1, 3, 5, 7): 0001-0007x2

  • Three-padded sequence, frames == (11, 13): 011,013

  • Two-padded sequence (1, 3, 5, 7, 11, 13, 102): 01-07x2,11,13,102

File Sequences

Members of a file sequence can be one of two formats:

  • base_name.frame_sequence.file_extension

  • frame_sequence.file_extension

Examples of valid file sequences:

  • my_little_pony.1-7x2.exr

  • /maya/is/very/strange/01-07x2,11,13,102.tif

  • C:\this\even\works\in\windows\billy.0001-0095.tga

seqls

seqls is the command line interface for the seqparse module.

usage: seqls [-h] [-a] [-H] [-l] [--maxdepth MAX_LEVELS]
             [--mindepth MIN_LEVELS] [-m] [-S]
             [search_path [search_path ...]]

Command line tool for listing file sequences. Upon installation of the package
this script will be accessable via ``seqls`` command on the command line of your
choice.

positional arguments:
  search_path           Paths that you'd like to search for file sequences.

optional arguments:
  -h, --help            show this help message and exit
  -a, --all             Do not ignore entries starting with '.'.
  -H, --human-readable  with -l/--long, print sizes in human readable format
                        (e.g., 1K 234M 2G).
  -l, --long            Use a long listing format.
  --maxdepth MAX_LEVELS
                        Descend at most levels (a non-negative integer)
                        MAX_LEVELS of directories below the starting-points.
                        '--maxdepth 0' means scan the starting-points
                        themselves.
  --mindepth MIN_LEVELS
                        Do not scan at levels less than MIN_LEVELS (a non-
                        negative integer). '--mindepth 1' means scan all
                        levels except the starting-points.
  -m, --missing         Whether to invert output file sequences to only report
                        the missing frames.
  -S, --seqs-only       Whether to filter out all non-sequence files.
  -v, --version         Print the version and exit.

Most of the functionality is self-explanatory, but the -m/--missing option is probably the most useful to users generating large sequences of frames on multiple servers.

Say you’re creating imagery for the latest superhero movie – and your render job crashed some time in the early morning.

You’re expecting to see something like this …

superhero_cape_v0001.0001-1000.exr

… but not everything rendered.

$ cd /renders/superhero_cape_v0001
$ seqls
superhero_cape_v0001.0001-0500,0600-0800,0990-1000x5.exr

You can easily figure out the missing frames, though, with the --missing option:

$ seqls --missing
superhero_cape_v0001.0501-0599,0801,0991-0994,0996-0999.exr

The module

Using the module is fairly simple:

  1. Instantiate a parser (Seqparse instance).

  2. Add files to the parser either

    • via the add_file method, or

    • by scanning a list of locations on disk via the scan_path method.

  3. Create an iterator for all file sequences (FileSequence instances) and singletons (File instances).

  4. Profit.

Example (taken from the Seqparse docstring):

With the following file structure ...

    test_dir/
        TEST_DIR.0001.tif
        TEST_DIR.0002.tif
        TEST_DIR.0003.tif
        TEST_DIR.0004.tif
        TEST_DIR.0010.tif
        SINGLETON.jpg

>>> from seqparse.seqparse import Seqparse
>>> parser = Seqparse()
>>> parser.scan_path("test_dir")
>>> for item in parser.output():
...     print str(item)
...
test_dir/TEST_DIR.0001-0004,0010.tif
test_dir/SINGLETON.jpg
>>> for item in parser.output(seqs_only=True):
...     print str(item)
...
test_dir/TEST_DIR.0001-0004,0010.tif
>>> for item in parser.output(missing=True):
...     print str(item)
...
test_dir/TEST_DIR.0005-0009.tif

Useful Classes

FrameSequence instances are pretty useful on their own.

>>> from seqparse import get_sequence
>>> seq = get_sequence([1, 2, 3, 4, 8])
>>> print repr(seq)
FrameSequence(pad=4, frames=set([1, 2, 3, 4, 8]))
>>> print seq
0001-0005,0008
>>> for frame in seq:
...     print frame
...
0001
0002
0003
0004
0010
>>> for frame in seq.invert():
...     print frame
...
0005
0006
0007

As are FileSequence instances (which behave similarly; check class documentation for details).

Roadmap

  1. v0.7.0

    1. Get around to setting up full coverage for the container classes.

  2. v1.0.0

    1. Release.

Current Tasks

  1. Add flag to Seqparse so that it knows when it’s supposed to test if files actually exist (ie, when it’s launched from seqls).

  2. Add output testing for FileSequenceContainer instances.

Final Notes

There’re still a number of things I’d like to do to make the class interfaces a bit more standardized (see my goals for the v0.7.0 release above), but aside from that I’m moderately happy with this code.

Lemme know if you have any requests/complaints/suggestions!

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