# -*- Mode: python; tab-width: 4; indent-tabs-mode:nil; coding: utf-8 -*-
# vim: tabstop=4 expandtab shiftwidth=4 softtabstop=4
#
# MDAnalysis --- https://www.mdanalysis.org
# Copyright (c) 2006-2017 The MDAnalysis Development Team and contributors
# (see the file AUTHORS for the full list of names)
#
# Released under the GNU Public Licence, v2 or any higher version
#
# Please cite your use of MDAnalysis in published work:
#
# 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
# simulations. In S. Benthall and S. Rostrup editors, Proceedings of the 15th
# Python in Science Conference, pages 102-109, Austin, TX, 2016. SciPy.
# doi: 10.25080/majora-629e541a-00e
#
# 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
#
"""\
=========================================================
Core object: Universe --- :mod:`MDAnalysis.core.universe`
=========================================================
The :class:`~MDAnalysis.core.universe.Universe` class ties a topology
and a trajectory together. Almost all code in MDAnalysis starts with a
``Universe``.
Normally, a ``Universe`` is created from files::
import MDAnalysis as mda
u = mda.Universe("topology.psf", "trajectory.dcd")
In order to construct new simulation system it is also convenient to
construct a ``Universe`` from existing
:class:`~MDAnalysis.core.group.AtomGroup` instances with the
:func:`Merge` function.
Working with Universes
======================
Quick segid selection
---------------------
.. deprecated:: 0.16.2
Instant selectors will be removed in the 1.0 release. See issue `#1377
<https://github.com/MDAnalysis/mdanalysis/issues/1377>`_ for more details.
If the loaded topology provided segids, then these are made accessible
as attributes of the Universe. If the segid starts with a number such
as '4AKE', the letter 's' will be prepended to the segid.
For example::
import MDAnalysis as mda
from MDAnalysisTests.datafiles import PSF, DCD
u = mda.Universe(PSF, DCD)
u.select_atoms('segid 4AKE') # selects all segments with segid 4AKE
If only a single segment has that segid then a Segment object will
be returned, otherwise a SegmentGroup will be returned.
Classes
=======
.. autoclass:: Universe
:members:
Functions
=========
.. autofunction:: Merge
"""
from __future__ import absolute_import
from six.moves import range
import six
import errno
import numpy as np
import logging
import copy
import warnings
import collections
import MDAnalysis
import sys
# When used in an MPI environment with Infiniband, importing MDAnalysis may
# trigger an MPI warning because importing the uuid module triggers a call to
# os.fork(). This happens if MPI_Init() has been called prior to importing
# MDAnalysis. The problem is actually caused by the uuid module and not by
# MDAnalysis itself. Python 3.7 fixes the problem. However, for Python < 3.7,
# the uuid module works perfectly fine with os.fork() disabled during import.
# A clean solution is therefore simply to disable os.fork() prior to importing
# the uuid module and to re-enable it afterwards.
import os
# Windows doesn't have os.fork so can ignore
# the issue for that platform
if sys.version_info >= (3, 7) or os.name == 'nt':
import uuid
else:
_os_dot_fork, os.fork = os.fork, None
import uuid
os.fork = _os_dot_fork
del _os_dot_fork
from .. import _ANCHOR_UNIVERSES, _TOPOLOGY_ATTRS, _PARSERS
from ..exceptions import NoDataError
from ..lib import util
from ..lib.log import ProgressMeter
from ..lib.util import cached, NamedStream, isstream
from ..lib.mdamath import find_fragments
from . import groups
from ._get_readers import get_reader_for, get_parser_for
from .groups import (ComponentBase, GroupBase,
Atom, Residue, Segment,
AtomGroup, ResidueGroup, SegmentGroup)
from .topology import Topology
from .topologyattrs import AtomAttr, ResidueAttr, SegmentAttr
logger = logging.getLogger("MDAnalysis.core.universe")
[docs]class Universe(object):
"""The MDAnalysis Universe contains all the information describing the system.
The system always requires a *topology* file --- in the simplest case just
a list of atoms. This can be a CHARMM/NAMD PSF file or a simple coordinate
file with atom informations such as XYZ, PDB, Gromacs GRO, or CHARMM
CRD. See :ref:`Supported topology formats` for what kind of topologies can
be read.
A trajectory provides coordinates; the coordinates have to be ordered in
the same way as the list of atoms in the topology. A trajectory can be a
single frame such as a PDB, CRD, or GRO file, or it can be a MD trajectory
(in CHARMM/NAMD/LAMMPS DCD, Gromacs XTC/TRR, or generic XYZ format). See
:ref:`Supported coordinate formats` for what can be read as a
"trajectory".
As a special case, when the topology is a file that contains atom
information *and* coordinates (such as XYZ, PDB, GRO or CRD, see
:ref:`Supported coordinate formats`) then the coordinates are immediately
loaded from the "topology" file unless a trajectory is supplied.
Examples for setting up a universe::
u = Universe(topology, trajectory) # read system from file(s)
u = Universe(pdbfile) # read atoms and coordinates from PDB or GRO
u = Universe(topology, [traj1, traj2, ...]) # read from a list of trajectories
u = Universe(topology, traj1, traj2, ...) # read from multiple trajectories
Load new data into a universe (replaces old trajectory and does *not* append)::
u.load_new(trajectory) # read from a new trajectory file
Select atoms, with syntax similar to CHARMM (see
:class:`~Universe.select_atoms` for details)::
u.select_atoms(...)
Parameters
----------
topology : str, Topology object or stream
A CHARMM/XPLOR PSF topology file, PDB file or Gromacs GRO file; used to
define the list of atoms. If the file includes bond information,
partial charges, atom masses, ... then these data will be available to
MDAnalysis. A "structure" file (PSF, PDB or GRO, in the sense of a
topology) is always required. Alternatively, an existing
:class:`MDAnalysis.core.topology.Topology` instance may also be given.
topology_format
Provide the file format of the topology file; ``None`` guesses it from
the file extension [``None``] Can also pass a subclass of
:class:`MDAnalysis.topology.base.TopologyReaderBase` to define a custom
reader to be used on the topology file.
format
Provide the file format of the coordinate or trajectory file; ``None``
guesses it from the file extension. Note that this keyword has no
effect if a list of file names is supplied because the "chained" reader
has to guess the file format for each individual list member.
[``None``] Can also pass a subclass of
:class:`MDAnalysis.coordinates.base.ProtoReader` to define a custom
reader to be used on the trajectory file.
all_coordinates : bool
If set to ``True`` specifies that if more than one filename is passed
they are all to be used, if possible, as coordinate files (employing a
:class:`MDAnalysis.coordinates.chain.ChainReader`). [``False``] The
default behavior is to take the first file as a topology and the
remaining as coordinates. The first argument will always always be used
to infer a topology regardless of *all_coordinates*. This parameter is
ignored if only one argument is passed.
guess_bonds : bool, optional
Once Universe has been loaded, attempt to guess the connectivity
between atoms. This will populate the .bonds .angles and .dihedrals
attributes of the Universe.
vdwradii : dict, optional
For use with *guess_bonds*. Supply a dict giving a vdwradii for each
atom type which are used in guessing bonds.
is_anchor : bool, optional
When unpickling instances of
:class:`MDAnalysis.core.groups.AtomGroup` existing Universes are
searched for one where to anchor those atoms. Set to ``False`` to
prevent this Universe from being considered. [``True``]
anchor_name : str, optional
Setting to other than ``None`` will cause
:class:`MDAnalysis.core.groups.AtomGroup` instances pickled from the
Universe to only unpickle if a compatible Universe with matching
*anchor_name* is found. Even if *anchor_name* is set *is_anchor* will
still be honored when unpickling.
transformations: function or list, optional
Provide a list of transformations that you wish to apply to the
trajectory upon reading. Transformations can be found in
:mod:`MDAnalysis.transformations`, or can be user-created.
in_memory
After reading in the trajectory, transfer it to an in-memory
representations, which allow for manipulation of coordinates.
in_memory_step
Only read every nth frame into in-memory representation.
continuous : bool, optional
The `continuous` option is used by the
:mod:`ChainReader<MDAnalysis.coordinates.chain>`, which contains the
functionality to treat independent trajectory files as a single virtual
trajectory.
Attributes
----------
trajectory
currently loaded trajectory reader;
dimensions
current system dimensions (simulation unit cell, if set in the
trajectory)
atoms, residues, segments
master Groups for each topology level
bonds, angles, dihedrals
master ConnectivityGroups for each connectivity type
"""
def __init__(self, *args, **kwargs):
# Store the segments for the deprecated instant selector feature.
# This attribute has to be defined early to avoid recursion in
# __getattr__.
self._instant_selectors = {}
# hold on to copy of kwargs; used by external libraries that
# reinitialize universes
self._kwargs = copy.deepcopy(kwargs)
# managed attribute holding Reader
self._trajectory = None
self._cache = {}
if not args:
# create an empty universe
self._topology = None
self.atoms = None
else:
topology_format = kwargs.pop('topology_format', None)
if len(args) == 1:
# special hacks to treat a coordinate file as a coordinate AND
# topology file
if kwargs.get('format', None) is None:
kwargs['format'] = topology_format
elif topology_format is None:
topology_format = kwargs.get('format', None)
# if we're given a Topology object, we don't need to parse anything
if isinstance(args[0], Topology):
self._topology = args[0]
self.filename = None
else:
if isinstance(args[0], NamedStream):
self.filename = args[0]
elif isstream(args[0]):
filename = None
if hasattr(args[0], 'name'):
filename = args[0].name
self.filename = NamedStream(args[0], filename)
else:
self.filename = args[0]
parser = get_parser_for(self.filename, format=topology_format)
try:
with parser(self.filename) as p:
self._topology = p.parse(**kwargs)
except (IOError, OSError) as err:
# There are 2 kinds of errors that might be raised here:
# one because the file isn't present
# or the permissions are bad, second when the parser fails
if (err.errno is not None and
errno.errorcode[err.errno] in ['ENOENT', 'EACCES']):
# Runs if the error is propagated due to no permission / file not found
six.reraise(*sys.exc_info())
else:
# Runs when the parser fails
raise IOError(
"Failed to load from the topology file {0}"
" with parser {1}.\n"
"Error: {2}".format(self.filename, parser, err))
except (ValueError, NotImplementedError) as err:
raise ValueError(
"Failed to construct topology from file {0}"
" with parser {1}.\n"
"Error: {2}".format(self.filename, parser, err))
# generate and populate Universe version of each class
self._generate_from_topology()
# Load coordinates
if len(args) == 1 or kwargs.get('all_coordinates', False):
if self.filename is None:
# If we got the topology as a Topology object, then we
# cannot read coordinates from it.
coordinatefile = args[1:]
else:
# Can the topology file also act as coordinate file?
try:
_ = get_reader_for(self.filename,
format=kwargs.get('format', None))
except ValueError:
coordinatefile = args[1:]
else:
coordinatefile = (self.filename,) + args[1:]
else:
coordinatefile = args[1:]
if not coordinatefile:
coordinatefile = None
self.load_new(coordinatefile, **kwargs)
# parse transformations
trans_arg = kwargs.pop('transformations', None)
if trans_arg:
transforms =[trans_arg] if callable(trans_arg) else trans_arg
self.trajectory.add_transformations(*transforms)
# Check for guess_bonds
if kwargs.pop('guess_bonds', False):
self.atoms.guess_bonds(vdwradii=kwargs.pop('vdwradii', None))
# None causes generic hash to get used.
# We store the name ieven if is_anchor is False in case the user later
# wants to make the universe an anchor.
self._anchor_name = kwargs.get('anchor_name', None)
# Universes are anchors by default
self.is_anchor = kwargs.get('is_anchor', True)
[docs] def copy(self):
"""Return an independent copy of this Universe"""
new = self.__class__(self._topology.copy())
new.trajectory = self.trajectory.copy()
return new
def _generate_from_topology(self):
# generate Universe version of each class
# AG, RG, SG, A, R, S
self._class_bases, self._classes = groups.make_classes()
# Put Group level stuff from topology into class
for attr in self._topology.attrs:
self._process_attr(attr)
# Generate atoms, residues and segments.
# These are the first such groups generated for this universe, so
# there are no cached merged classes yet. Otherwise those could be
# used directly to get a (very) small speedup. (Only really pays off
# the readability loss if instantiating millions of AtomGroups at
# once.)
self.atoms = AtomGroup(np.arange(self._topology.n_atoms), self)
self.residues = ResidueGroup(
np.arange(self._topology.n_residues), self)
self.segments = SegmentGroup(
np.arange(self._topology.n_segments), self)
# Update Universe namespace with segids
# Many segments can have same segid, so group together first
#
# DEPRECATED in 0.16.2
# REMOVE in 1.0
# See https://github.com/MDAnalysis/mdanalysis/issues/1377
try:
# returns dict of segid:segment
segids = self.segments.groupby('segids')
except AttributeError:
# no segids, don't do this step
pass
else:
for segid, segment in segids.items():
if not segid: # ignore blank segids
continue
# cannot start attribute with number
if segid[0].isdigit():
# prefix 's' if starts with number
name = 's' + segid
else:
name = segid
# if len 1 SegmentGroup, convert to Segment
if len(segment) == 1:
segment = segment[0]
self._instant_selectors[name] = segment
[docs] @classmethod
def empty(cls, n_atoms, n_residues=None, n_segments=None,
atom_resindex=None, residue_segindex=None,
trajectory=False, velocities=False, forces=False):
"""Create a blank Universe
Useful for building a Universe without requiring existing files,
for example for system building.
If `trajectory` is set to True, a
:class:`MDAnalysis.coordinates.memory.MemoryReader` will be
attached to the Universe.
Parameters
----------
n_atoms : int
number of Atoms in the Universe
n_residues : int, optional
number of Residues in the Universe, defaults to 1
n_segments : int, optional
number of Segments in the Universe, defaults to 1
atom_resindex : array like, optional
mapping of atoms to residues, e.g. with 6 atoms,
`atom_resindex=[0, 0, 1, 1, 2, 2]` would put 2 atoms
into each of 3 residues.
residue_segindex : array like, optional
mapping of residues to segments
trajectory : bool, optional
if True, attaches a :class:`MDAnalysis.coordinates.memory.MemoryReader`
allowing coordinates to be set and written. Default is False
velocities : bool, optional
include velocities in the :class:`MDAnalysis.coordinates.memory.MemoryReader`
forces : bool, optional
include forces in the :class:`MDAnalysis.coordinates.memory.MemoryReader`
Returns
-------
MDAnalysis.Universe object
Examples
--------
For example to create a new Universe with 6 atoms in 2 residues, with
positions for the atoms and a mass attribute:
>>> u = mda.Universe.empty(6, 2,
atom_resindex=np.array([0, 0, 0, 1, 1, 1]),
trajectory=True,
)
>>> u.add_TopologyAttr('masses')
.. versionadded:: 0.17.0
.. versionchanged:: 0.19.0
The attached Reader when trajectory=True is now a MemoryReader
"""
if n_residues is None:
n_residues = 1
elif atom_resindex is None:
warnings.warn(
'Multiple residues specified but no atom_resindex given. '
'All atoms will be placed in first Residue.',
UserWarning)
if n_segments is None:
n_segments = 1
elif residue_segindex is None:
warnings.warn(
'Multiple segments specified but no segment_resindex given. '
'All residues will be placed in first Segment',
UserWarning)
top = Topology(n_atoms, n_residues, n_segments,
atom_resindex=atom_resindex,
residue_segindex=residue_segindex,
)
u = cls(top)
if trajectory:
coords = np.zeros((1, n_atoms, 3), dtype=np.float32)
dims = np.zeros(6, dtype=np.float32)
vels = np.zeros_like(coords) if velocities else None
forces = np.zeros_like(coords) if forces else None
# grab and attach a MemoryReader
u.trajectory = get_reader_for(coords)(
coords, order='fac', n_atoms=n_atoms,
dimensions=dims, velocities=vels, forces=forces)
return u
def __getattr__(self, key):
# This implements the instant selector of segments from a Universe.
# It is implemented as __getattr__ so a deprecation warning can be
# issued when the feature is used. Instant selectors are deprecated
# since version 0.16.2 and are tareted to be deleted in version 1.0.
# self._instant_selectors is populated in self._process_attr and
# created at the beginning of __init__.
try:
segment = self._instant_selectors[key]
except KeyError:
raise AttributeError('No attribute "{}".'.format(key))
else:
warnings.warn("Instant selector Universe.<segid> "
"is deprecated and will be removed in 1.0. "
"Use SegmentGroup[SegmentGroup.segids == '<segid>'] "
"instead.",
DeprecationWarning)
return segment
@property
def universe(self):
# for Writer.write(universe), see Issue 49
# Encapsulation in an accessor prevents the Universe from
# having to keep a reference to itself,
# which might be undesirable if it has a __del__ method.
# It is also cleaner than a weakref.
return self
[docs] def load_new(self, filename, format=None, in_memory=False, **kwargs):
"""Load coordinates from `filename`.
The file format of `filename` is autodetected from the file name suffix
or can be explicitly set with the `format` keyword. A sequence of files
can be read as a single virtual trajectory by providing a list of
filenames.
Parameters
----------
filename : str or list
the coordinate file (single frame or trajectory) *or* a list of
filenames, which are read one after another.
format : str or list or object (optional)
provide the file format of the coordinate or trajectory file;
``None`` guesses it from the file extension. Note that this
keyword has no effect if a list of file names is supplied because
the "chained" reader has to guess the file format for each
individual list member [``None``]. Can also pass a subclass of
:class:`MDAnalysis.coordinates.base.ProtoReader` to define a custom
reader to be used on the trajectory file.
in_memory : bool (optional)
Directly load trajectory into memory with the
:class:`~MDAnalysis.coordinates.memory.MemoryReader`
.. versionadded:: 0.16.0
**kwargs : dict
Other kwargs are passed to the trajectory reader (only for
advanced use)
Returns
-------
universe : Universe
Raises
------
TypeError if trajectory format can not be
determined or no appropriate trajectory reader found
.. versionchanged:: 0.8
If a list or sequence that is provided for `filename` only contains
a single entry then it is treated as single coordinate file. This
has the consequence that it is not read by the
:class:`~MDAnalysis.coordinates.chain.ChainReader` but directly by
its specialized file format reader, which typically has more
features than the
:class:`~MDAnalysis.coordinates.chain.ChainReader`.
.. versionchanged:: 0.17.0
Now returns a :class:`Universe` instead of the tuple of file/array
and detected file type.
"""
# filename==None happens when only a topology is provided
if filename is None:
return self
if len(util.asiterable(filename)) == 1:
# make sure a single filename is not handed to the ChainReader
filename = util.asiterable(filename)[0]
logger.debug("Universe.load_new(): loading {0}...".format(filename))
try:
reader = get_reader_for(filename, format=format)
except ValueError as err:
raise TypeError(
"Cannot find an appropriate coordinate reader for file '{0}'.\n"
" {1}".format(filename, err))
# supply number of atoms for readers that cannot do it for themselves
kwargs['n_atoms'] = self.atoms.n_atoms
self.trajectory = reader(filename, **kwargs)
if self.trajectory.n_atoms != len(self.atoms):
raise ValueError("The topology and {form} trajectory files don't"
" have the same number of atoms!\n"
"Topology number of atoms {top_n_atoms}\n"
"Trajectory: {fname} Number of atoms {trj_n_atoms}".format(
form=self.trajectory.format,
top_n_atoms=len(self.atoms),
fname=filename,
trj_n_atoms=self.trajectory.n_atoms))
if in_memory:
self.transfer_to_memory(step=kwargs.get("in_memory_step", 1))
return self
[docs] def transfer_to_memory(self, start=None, stop=None, step=None,
verbose=False):
"""Transfer the trajectory to in memory representation.
Replaces the current trajectory reader object with one of type
:class:`MDAnalysis.coordinates.memory.MemoryReader` to support in-place
editing of coordinates.
Parameters
----------
start: int, optional
start reading from the nth frame.
stop: int, optional
read upto and excluding the nth frame.
step : int, optional
Read in every nth frame. [1]
verbose : bool, optional
Will print the progress of loading trajectory to memory, if
set to True. Default value is False.
.. versionadded:: 0.16.0
"""
from ..coordinates.memory import MemoryReader
if not isinstance(self.trajectory, MemoryReader):
n_frames = len(range(
*self.trajectory.check_slice_indices(start, stop, step)
))
n_atoms = len(self.atoms)
pm_format = '{step}/{numsteps} frames copied to memory (frame {frame})'
pm = ProgressMeter(n_frames, interval=1,
verbose=verbose, format=pm_format)
coordinates = np.zeros((n_frames, n_atoms, 3), dtype=np.float32)
ts = self.trajectory.ts
has_vels = ts.has_velocities
has_fors = ts.has_forces
has_dims = ts.dimensions is not None
velocities = np.zeros_like(coordinates) if has_vels else None
forces = np.zeros_like(coordinates) if has_fors else None
dimensions = (np.zeros((n_frames, 6), dtype=np.float32)
if has_dims else None)
for i, ts in enumerate(self.trajectory[start:stop:step]):
np.copyto(coordinates[i], ts.positions)
if has_vels:
np.copyto(velocities[i], ts.velocities)
if has_fors:
np.copyto(forces[i], ts.forces)
if has_dims:
np.copyto(dimensions[i], ts.dimensions)
pm.echo(i, frame=ts.frame)
# Overwrite trajectory in universe with an MemoryReader
# object, to provide fast access and allow coordinates
# to be manipulated
if step is None:
step = 1
self.trajectory = MemoryReader(
coordinates,
dimensions=dimensions,
dt=self.trajectory.ts.dt * step,
filename=self.trajectory.filename,
velocities=velocities,
forces=forces,
)
# python 2 doesn't allow an efficient splitting of kwargs in function
# argument signatures.
# In python3-only we'd be able to explicitly define this function with
# something like (sel, *othersels, updating=False, **selgroups)
[docs] def select_atoms(self, *args, **kwargs):
"""Select atoms.
See Also
--------
:meth:`MDAnalysis.core.groups.AtomGroup.select_atoms`
"""
return self.atoms.select_atoms(*args, **kwargs)
@property
def bonds(self):
"""Bonds between atoms"""
return self.atoms.bonds
@property
def angles(self):
"""Angles between atoms"""
return self.atoms.angles
@property
def dihedrals(self):
"""Dihedral angles between atoms"""
return self.atoms.dihedrals
@property
def impropers(self):
"""Improper dihedral angles between atoms"""
return self.atoms.impropers
@property
def anchor_name(self):
return self._gen_anchor_hash()
@anchor_name.setter
def anchor_name(self, name):
self.remove_anchor() # clear any old anchor
self._anchor_name = str(name) if not name is None else name
self.make_anchor() # add anchor again
def _gen_anchor_hash(self):
# hash used for anchoring.
# Try and use anchor_name, else use (and store) uuid
if self._anchor_name is not None:
return self._anchor_name
else:
try:
return self._anchor_uuid
except AttributeError:
# store this so we can later recall it if needed
self._anchor_uuid = uuid.uuid4()
return self._anchor_uuid
@property
def is_anchor(self):
"""Is this Universe an anchoring for unpickling AtomGroups"""
return self._gen_anchor_hash() in _ANCHOR_UNIVERSES
@is_anchor.setter
def is_anchor(self, new):
if new:
self.make_anchor()
else:
self.remove_anchor()
[docs] def remove_anchor(self):
"""Remove this Universe from the possible anchor list for unpickling"""
_ANCHOR_UNIVERSES.pop(self._gen_anchor_hash(), None)
def make_anchor(self):
_ANCHOR_UNIVERSES[self._gen_anchor_hash()] = self
def __repr__(self):
# return "<Universe with {n_atoms} atoms{bonds}>".format(
# n_atoms=len(self.atoms),
# bonds=" and {0} bonds".format(len(self.bonds)) if self.bonds else "")
return "<Universe with {n_atoms} atoms>".format(
n_atoms=len(self.atoms))
def __getstate__(self):
raise NotImplementedError
def __setstate__(self, state):
raise NotImplementedError
# Properties
@property
def dimensions(self):
"""Current dimensions of the unitcell"""
return self.coord.dimensions
@dimensions.setter
def dimensions(self, box):
"""Set dimensions if the Timestep allows this
.. versionadded:: 0.9.0
"""
# Add fancy error handling here or use Timestep?
self.coord.dimensions = box
@property
def coord(self):
"""Reference to current timestep and coordinates of universe.
The raw trajectory coordinates are :attr:`Universe.coord.positions`,
represented as a :class:`numpy.float32` array.
Because :attr:`coord` is a reference to a
:class:`~MDAnalysis.coordinates.base.Timestep`, it changes its contents
while one is stepping through the trajectory.
.. Note::
In order to access the coordinates it is better to use the
:meth:`AtomGroup.positions` method; for instance, all coordinates of
the Universe as a numpy array: :meth:`Universe.atoms.positions`.
"""
return self.trajectory.ts
@property
def kwargs(self):
"""keyword arguments used to initialize this universe"""
return copy.deepcopy(self._kwargs)
@property
def trajectory(self):
"""Reference to trajectory reader object containing trajectory data."""
if self._trajectory is not None:
return self._trajectory
else:
raise AttributeError("No trajectory loaded into Universe")
@trajectory.setter
def trajectory(self, value):
del self._trajectory # guarantees that files are closed (?)
self._trajectory = value
[docs] def add_TopologyAttr(self, topologyattr, values=None):
"""Add a new topology attribute to the Universe
Adding a TopologyAttribute to the Universe makes it available to
all AtomGroups etc throughout the Universe.
Parameters
----------
topologyattr : TopologyAttr or string
Either a MDAnalysis TopologyAttr object or the name of a possible
topology attribute.
values : np.ndarray, optional
If initiating an attribute from a string, the initial values to
use. If not supplied, the new TopologyAttribute will have empty
or zero values.
Example
-------
For example to add bfactors to a Universe:
>>> u.add_TopologyAttr('bfactors')
>>> u.atoms.bfactors
array([ 0., 0., 0., ..., 0., 0., 0.])
.. versionchanged:: 0.17.0
Can now also add TopologyAttrs with a string of the name of the
attribute to add (eg 'charges'), can also supply initial values
using values keyword.
"""
if isinstance(topologyattr, six.string_types):
try:
tcls = _TOPOLOGY_ATTRS[topologyattr]
except KeyError:
raise ValueError(
"Unrecognised topology attribute name: '{}'."
" Possible values: '{}'\n"
"To raise an issue go to: http://issues.mdanalysis.org"
"".format(
topologyattr, ', '.join(sorted(_TOPOLOGY_ATTRS.keys())))
)
else:
topologyattr = tcls.from_blank(
n_atoms=self._topology.n_atoms,
n_residues=self._topology.n_residues,
n_segments=self._topology.n_segments,
values=values)
self._topology.add_TopologyAttr(topologyattr)
self._process_attr(topologyattr)
def _process_attr(self, attr):
"""Squeeze a topologyattr for its information
Grabs:
- Group properties (attribute access)
- Component properties
- Transplant methods
"""
n_dict = {'atom': self._topology.n_atoms,
'residue': self._topology.n_residues,
'segment': self._topology.n_segments}
logger.debug("_process_attr: Adding {0} to topology".format(attr))
if (attr.per_object is not None and len(attr) != n_dict[attr.per_object]):
raise ValueError('Length of {attr} does not'
' match number of {obj}s.\n'
'Expect: {n:d} Have: {m:d}'.format(
attr=attr.attrname,
obj=attr.per_object,
n=n_dict[attr.per_object],
m=len(attr)))
for cls in attr.target_classes:
self._class_bases[cls]._add_prop(attr)
# TODO: Try and shove this into cls._add_prop
# Group transplants
for cls in (Atom, Residue, Segment, GroupBase,
AtomGroup, ResidueGroup, SegmentGroup):
for funcname, meth in attr.transplants[cls]:
setattr(self._class_bases[cls], funcname, meth)
# Universe transplants
for funcname, meth in attr.transplants['Universe']:
setattr(self.__class__, funcname, meth)
[docs] def add_Residue(self, segment=None, **attrs):
"""Add a new Residue to this Universe
New Residues will not contain any Atoms, but can be assigned to Atoms
as per usual. If the Universe contains multiple segments, this must
be specified as a keyword.
Parameters
----------
segment : MDAnalysis.Segment
If there are multiple segments, then the Segment that the new
Residue will belong in must be specified.
attrs : dict
For each Residue attribute, the value for the new Residue must be
specified
Returns
-------
A reference to the new Residue
Raises
------
NoDataError
If any information was missing. This happens before any changes have
been made, ie the change is rolled back.
Example
-------
Adding a new GLY residue, then placing atoms within it:
>>> newres = u.add_Residue(segment=u.segments[0], resid=42, resname='GLY')
>>> u.atoms[[1, 2, 3]].residues = newres
>>> u.select_atoms('resname GLY and resid 42')
<AtomGroup with 3 atoms>
"""
if len(self.segments) == 1: # if only one segment, use this
segment = self.segments[0]
if segment is None:
raise NoDataError("")
# pass this information to the topology
residx = self._topology.add_Residue(segment, **attrs)
# resize my residues
self.residues = ResidueGroup(np.arange(self._topology.n_residues), self)
# return the new residue
return self.residues[residx]
[docs] def add_Segment(self, **attrs):
"""Add a new Segment to this Universe
Parameters
----------
attrs : dict
For each Segment attribute as a key, give the value in the new
Segment
Returns
-------
A reference to the new Segment
Raises
------
NoDataError
If any attributes were not specified as a keyword.
"""
# pass this information to the topology
segidx = self._topology.add_Segment(**attrs)
# resize my segments
self.segments = SegmentGroup(np.arange(self._topology.n_segments), self)
# return the new segment
return self.segments[segidx]
# TODO: Maybe put this as a Bond attribute transplant
# Problems: Can we transplant onto Universe?
# Probably a smarter way to do this too, could generate
# these on demand *per atom*.
# Wouldn't then need the Universe linkage here
#
# Alternate idea: Bonds Attribute generates a Fragments
# Attribute (ie, 2 for the price of 1)
# Fragments then gets its own Class/namespace/jazz.
@property
@cached('fragments')
def _fragdict(self):
"""
.. versionadded:: 0.9.0
.. versionchanged:: 0.16.0
Fragment atoms are sorted by their index, and framgents are sorted
by their first atom index so their order is predictable.
.. versionchanged:: 0.19.0
Uses faster C++ implementation
.. versionchanged:: 0.20.0
* _fragdict keys are now atom indices instead of Atoms
* _fragdict items are now a namedtuple ``fraginfo(ix, fragment)``
storing the fragindex ``ix`` along with the fragment.
"""
atoms = self.atoms.ix
bonds = self.atoms.bonds.to_indices()
frag_indices = find_fragments(atoms, bonds)
frags = tuple([AtomGroup(np.sort(ix), self) for ix in frag_indices])
fragdict = {}
fraginfo = collections.namedtuple('fraginfo', 'ix, fragment')
for i, f in enumerate(frags):
for a in f:
fragdict[a.ix] = fraginfo(i, f)
return fragdict
# TODO: what is the point of this function???
def as_Universe(*args, **kwargs):
"""Return a universe from the input arguments.
1. If the first argument is a universe, just return it::
as_Universe(universe) --> universe
2. Otherwise try to build a universe from the first or the first
and second argument::
as_Universe(PDB, **kwargs) --> Universe(PDB, **kwargs)
as_Universe(PSF, DCD, **kwargs) --> Universe(PSF, DCD, **kwargs)
as_Universe(*args, **kwargs) --> Universe(*args, **kwargs)
Returns
-------
:class:`~MDAnalysis.core.groups.Universe`
"""
if len(args) == 0:
raise TypeError("as_Universe() takes at least one argument (%d given)" % len(args))
elif len(args) == 1 and isinstance(args[0], Universe):
return args[0]
return Universe(*args, **kwargs)
[docs]def Merge(*args):
"""Create a new new :class:`Universe` from one or more
:class:`~MDAnalysis.core.groups.AtomGroup` instances.
Parameters
----------
*args : :class:`~MDAnalysis.core.groups.AtomGroup`
One or more AtomGroups.
Returns
-------
universe : :class:`Universe`
Raises
------
ValueError
Too few arguments or an AtomGroup is empty and
TypeError
Arguments are not :class:`AtomGroup` instances.
Notes
-----
The resulting :class:`Universe` will only inherit the common topology
attributes that all merged universes share.
:class:`AtomGroup` instances can come from different Universes, or can come
directly from a :meth:`~Universe.select_atoms` call.
:class:`Merge` can also be used with a single :class:`AtomGroup` if the
user wants to, for example, re-order the atoms in the :class:`Universe`.
If multiple :class:`AtomGroup` instances from the same :class:`Universe`
are given, the merge will first simply "add" together the
:class:`AtomGroup` instances.
Merging does not create a full trajectory but only a single structure even
if the input consists of one or more trajectories. However, one can use
the :class:`~MDAnalysis.coordinates.memory.MemoryReader` to construct a
trajectory for the new Universe as described under
:ref:`creating-in-memory-trajectory-label`.
Example
-------
In this example, protein, ligand, and solvent were externally prepared in
three different PDB files. They are loaded into separate :class:`Universe`
objects (where they could be further manipulated, e.g. renumbered,
relabeled, rotated, ...) The :func:`Merge` command is used to combine all
of them together::
u1 = Universe("protein.pdb")
u2 = Universe("ligand.pdb")
u3 = Universe("solvent.pdb")
u = Merge(u1.select_atoms("protein"), u2.atoms, u3.atoms)
u.atoms.write("system.pdb")
The complete system is then written out to a new PDB file.
.. versionchanged:: 0.9.0
Raises exceptions instead of assertion errors.
.. versionchanged:: 0.16.0
The trajectory is now a
:class:`~MDAnalysis.coordinates.memory.MemoryReader`.
"""
from ..topology.base import squash_by
if len(args) == 0:
raise ValueError("Need at least one AtomGroup for merging")
for a in args:
if not isinstance(a, groups.AtomGroup):
raise TypeError(repr(a) + " is not an AtomGroup")
for a in args:
if len(a) == 0:
raise ValueError("cannot merge empty AtomGroup")
# Create a new topology using the intersection of topology attributes
blank_topology_attrs = set(dir(Topology(attrs=[])))
common_attrs = set.intersection(*[set(dir(ag.universe._topology))
for ag in args])
tops = set(['bonds', 'angles', 'dihedrals', 'impropers'])
attrs = []
# Create set of attributes which are array-valued and can be simply
# concatenated together
common_array_attrs = common_attrs - blank_topology_attrs - tops
# Build up array-valued topology attributes including only attributes
# that all arguments' universes have
for attrname in common_array_attrs:
for ag in args:
attr = getattr(ag, attrname)
attr_class = type(getattr(ag.universe._topology, attrname))
if issubclass(attr_class, AtomAttr):
pass
elif issubclass(attr_class, ResidueAttr):
attr = getattr(ag.residues, attrname)
elif issubclass(attr_class, SegmentAttr):
attr = getattr(ag.segments, attrname)
else:
raise NotImplementedError("Don't know how to handle"
" TopologyAttr not subclassed"
" from AtomAttr, ResidueAttr,"
" or SegmentAttr.")
if type(attr) != np.ndarray:
raise TypeError('Encountered unexpected topology '
'attribute of type {}'.format(type(attr)))
try:
attr_array.extend(attr)
except NameError:
attr_array = list(attr)
attrs.append(attr_class(np.array(attr_array, dtype=attr.dtype)))
del attr_array
# Build up topology groups including only those that all arguments'
# universes have
for t in (tops & common_attrs):
offset = 0
bondidx = []
types = []
for ag in args:
# create a mapping scheme for this atomgroup
mapping = {a.index: i for i, a in enumerate(ag, start=offset)}
offset += len(ag)
tg = getattr(ag, t)
bonds_class = type(getattr(ag.universe._topology, t))
# Create a topology group of only bonds that are within this ag
# ie we don't want bonds that extend out of the atomgroup
tg = tg.atomgroup_intersection(ag, strict=True)
# Map them so they refer to our new indices
new_idx = [tuple([mapping[x] for x in entry]) for entry in tg.indices]
bondidx.extend(new_idx)
if hasattr(tg, '_bondtypes'):
types.extend(tg._bondtypes)
else:
types.extend([None]*len(tg))
if any(t is None for t in types):
attrs.append(bonds_class(bondidx))
else:
types = np.array(types, dtype='|S8')
attrs.append(bonds_class(bondidx, types))
# Renumber residue and segment indices
n_atoms = sum([len(ag) for ag in args])
residx = []
segidx = []
res_offset = 0
seg_offset = 0
for ag in args:
# create a mapping scheme for this atomgroup's parents
res_mapping = {r.resindex: i for i, r in enumerate(ag.residues,
start=res_offset)}
seg_mapping = {r.segindex: i for i, r in enumerate(ag.segments,
start=seg_offset)}
res_offset += len(ag.residues)
seg_offset += len(ag.segments)
# Map them so they refer to our new indices
residx.extend([res_mapping[x] for x in ag.resindices])
segidx.extend([seg_mapping[x] for x in ag.segindices])
residx = np.array(residx, dtype=np.int32)
segidx = np.array(segidx, dtype=np.int32)
_, _, [segidx] = squash_by(residx, segidx)
n_residues = len(set(residx))
n_segments = len(set(segidx))
top = Topology(n_atoms, n_residues, n_segments,
attrs=attrs,
atom_resindex=residx,
residue_segindex=segidx)
# Create and populate a universe
coords = np.vstack([a.positions for a in args])
u = Universe(top, coords[None, :, :],
format=MDAnalysis.coordinates.memory.MemoryReader)
return u
