Source code for MDAnalysis.selections.base
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# R. J. Gowers, M. Linke, J. Barnoud, T. J. E. Reddy, M. N. Melo, S. L. Seyler,
# D. L. Dotson, J. Domanski, S. Buchoux, I. M. Kenney, and O. Beckstein.
# MDAnalysis: A Python package for the rapid analysis of molecular dynamics
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# doi: 10.25080/majora-629e541a-00e
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# N. Michaud-Agrawal, E. J. Denning, T. B. Woolf, and O. Beckstein.
# MDAnalysis: A Toolkit for the Analysis of Molecular Dynamics Simulations.
# J. Comput. Chem. 32 (2011), 2319--2327, doi:10.1002/jcc.21787
#
"""
Base classes for the selection writers
======================================
Specialized SelectionWriters are derived from
:class:`SelectionWriterBase`. Override the :meth:`~SelectionWriterBase._write_head`,
:meth:`~SelectionWriterBase._translate`, and :meth:`~SelectionWriterBase._write_tail`
methods.
.. autoclass:: SelectionWriterBase
:members: __init__, write, _translate, _write_head, _write_tail, comment
.. autofunction:: join
"""
import os.path
from ..lib import util
from . import _SELECTION_WRITERS
[docs]def join(seq, string="", func=None):
"""Create a list from sequence.
*string* is appended to each element but the last.
*func* is applied to every element before appending *string*.
"""
if func is None:
func = lambda x: x
return [func(x) + string for x in seq[:-1]] + [func(seq[-1])]
class _Selectionmeta(type):
# Auto register upon class creation
def __init__(cls, name, bases, classdict):
type.__init__(type, name, bases, classdict)
try:
fmt = util.asiterable(classdict['format'])
except KeyError:
pass
else:
for f in fmt:
if f is None:
continue
f = f.upper()
_SELECTION_WRITERS[f] = cls
[docs]class SelectionWriterBase(metaclass=_Selectionmeta):
"""Export a selection in MDAnalysis to a format usable in an external package.
The :class:`SelectionWriterBase` writes a selection string to a file
that can be used in another package such as `VMD`_, `PyMOL`_,
`Gromacs`_ or `CHARMM`_. In this way, analysis and visualization
can be done with the best or most convenient tools at hand.
:class:`SelectionWriterBase` is a base class and child classes are
derived with the appropriate customizations for the package file
format.
.. _VMD: http://www.ks.uiuc.edu/Research/vmd/
.. _PyMol: http://www.pymol.org/
.. _CHARMM: http://www.charmm.org/
.. _Gromacs: http://www.gromacs.org/
.. versionchanged:: 0.11.0
Can now also write to a :class:`~MDAnalysis.lib.util.NamedStream` instead
of a normal file (using :class:`~MDAnalysis.lib.util.openany`).
.. versionchanged:: 0.16.0
Remove the `wa` mode. The file is now open when the instance is created
and closed with the :meth:`close` method or when exiting the `with`
statement.
"""
#: Name of the format.
format = None
#: Extension of output files.
ext = None
#: Special character to continue a line across a newline.
continuation = ''
#: Comment format string; should contain '%s' or ``None`` for no comments.
commentfmt = None
default_numterms = 8
[docs] def __init__(self, filename, mode="w", numterms=None, preamble=None, **kwargs):
"""Set up for writing to *filename*.
Parameters
----------
filename:
output file
mode:
create a new file ("w"), or append ("a") to existing file ["w"]
numterms:
number of individual index numbers per line for output
formats that write multiple entries in one line. If set
to 0 or ``False`` then no special formatting is done [8]
preamble:
string that is written as a comment at the top of the file []
kwargs:
use as defaults for :meth:`write`
"""
self.filename = util.filename(filename, ext=self.ext)
if not mode in ('a', 'w'):
raise ValueError("mode must be one of 'w', 'a', not {0!r}".format(mode))
self.mode = mode
self._current_mode = mode[0]
if numterms is None or numterms < 0:
self.numterms = self.default_numterms
elif numterms is False:
self.numterms = 0
else:
self.numterms = numterms
self.preamble = preamble
self.otherargs = kwargs # hack
self.number = 0
self._outfile = util.anyopen(self.filename, mode=self._current_mode)
self.write_preamble()
[docs] def comment(self, s):
"""Return string *s* interpolated into the comment format string.
If no :attr:`SelectionWriterBase.commentfmt` is defined (None) then the
empty string is returned because presumably there is no way to enter
comments into the file.
A newline is appended to non-empty strings.
"""
if self.commentfmt is None:
return ''
return self.commentfmt % s + '\n'
def write_preamble(self):
"""Write a header, depending on the file format."""
if self.preamble is None:
return
self._outfile.write(self.comment(self.preamble))
[docs] def write(self, selection, number=None, name=None, frame=None, mode=None):
"""Write selection to the output file.
Parameters
----------
selection:
a :class:`MDAnalysis.core.groups.AtomGroup`
number:
selection will be named "mdanalysis<number>"
(``None`` auto increments between writes; useful
when appending) [``None``]
name:
selection will be named *name* (instead of numbered) [``None``]
frame:
write selection of this frame (or the current one if
``None`` [``None``]
"""
u = selection.universe
if frame is not None:
u.trajectory[frame] # advance to frame
else:
try:
frame = u.trajectory.ts.frame
except AttributeError:
frame = 1 # should catch cases when we are analyzing a single PDB (?)
name = name or self.otherargs.get('name', None)
if name is None:
if number is None:
self.number += 1
number = self.number
name = "mdanalysis{number:03d}".format(**vars())
# build whole selection in one go (cleaner way to deal with
# to deal with line breaks after self.numterms entries)
# selection_list must contain entries to be joined with spaces or linebreaks
selection_terms = self._translate(selection.atoms)
step = self.numterms or len(selection.atoms)
out = self._outfile
self._write_head(out, name=name)
for iatom in range(0, len(selection.atoms), step):
line = selection_terms[iatom:iatom + step]
out.write(" ".join(line))
if len(line) == step and not iatom + step == len(selection.atoms):
out.write(' ' + self.continuation + '\n')
out.write(' ') # safe so that we don't have to put a space at the start of tail
self._write_tail(out)
out.write('\n') # always terminate with newline
def close(self):
"""Close the file
.. versionadded:: 0.16.0
"""
self._outfile.close()
[docs] def _translate(self, atoms, **kwargs):
"""Translate atoms into a list of native selection terms.
- build list of ALL selection terms as if this was a single line, e.g.
``['index 12 |', 'index 22 |', 'index 33']``
- only one term per atom!!
- terms *must* be strings
- something like::
" ".join(terms)
must work
"""
raise NotImplementedError
[docs] def _write_head(self, out, **kwargs):
"""Initial output to open file object *out*."""
pass # pylint: disable=unnecessary-pass
[docs] def _write_tail(self, out, **kwargs):
"""Last output to open file object *out*."""
pass # pylint: disable=unnecessary-pass
# Context manager support to match Coordinate writers
# all file handles use a with block in their write method, so these do nothing special
def __enter__(self):
return self
def __exit__(self, *exc):
self.close()