Source code for

"""Module to read and write atoms in cif file format.

See for a
description of the file format.  STAR extensions as save frames,
global blocks, nested loops and multi-data values are not supported.
The "latin-1" encoding is required by the IUCR specification.

import io
import re
import shlex
import warnings
from typing import Any, Dict, Iterator, List, Optional, Sequence, Tuple, Union

import numpy as np

from ase import Atoms
from ase.cell import Cell
from import format_unicode, handle_subscripts
from ase.spacegroup import crystal
from ase.spacegroup.spacegroup import Spacegroup, spacegroup_from_data
from ase.utils import iofunction

rhombohedral_spacegroups = {146, 148, 155, 160, 161, 166, 167}

old_spacegroup_names = {'Abm2': 'Aem2',
                        'Aba2': 'Aea2',
                        'Cmca': 'Cmce',
                        'Cmma': 'Cmme',
                        'Ccca': 'Ccc1'}

# CIF maps names to either single values or to multiple values via loops.
CIFDataValue = Union[str, int, float]
CIFData = Union[CIFDataValue, List[CIFDataValue]]

def convert_value(value: str) -> CIFDataValue:
    """Convert CIF value string to corresponding python type."""
    value = value.strip()
    if re.match('(".*")|(\'.*\')$', value):
        return handle_subscripts(value[1:-1])
    elif re.match(r'[+-]?\d+$', value):
        return int(value)
    elif re.match(r'[+-]?(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?$', value):
        return float(value)
    elif re.match(r'[+-]?(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?\(\d+\)$',
        return float(value[:value.index('(')])  # strip off uncertainties
    elif re.match(r'[+-]?(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?\(\d+$',
        warnings.warn(f'Badly formed number: "{value}"')
        return float(value[:value.index('(')])  # strip off uncertainties
        return handle_subscripts(value)

def parse_multiline_string(lines: List[str], line: str) -> str:
    """Parse semicolon-enclosed multiline string and return it."""
    assert line[0] == ';'
    strings = [line[1:].lstrip()]
    while True:
        line = lines.pop().strip()
        if line[:1] == ';':
    return '\n'.join(strings).strip()

def parse_singletag(lines: List[str], line: str) -> Tuple[str, CIFDataValue]:
    """Parse a CIF tag (entries starting with underscore). Returns
    a key-value pair."""
    kv = line.split(None, 1)
    if len(kv) == 1:
        key = line
        line = lines.pop().strip()
        while not line or line[0] == '#':
            line = lines.pop().strip()
        if line[0] == ';':
            value = parse_multiline_string(lines, line)
            value = line
        key, value = kv
    return key, convert_value(value)

def parse_cif_loop_headers(lines: List[str]) -> Iterator[str]:
    while lines:
        line = lines.pop()
        tokens = line.split()

        if len(tokens) == 1 and tokens[0].startswith('_'):
            header = tokens[0].lower()
            yield header
            lines.append(line)  # 'undo' pop

def parse_cif_loop_data(lines: List[str],
                        ncolumns: int) -> List[List[CIFDataValue]]:
    columns: List[List[CIFDataValue]] = [[] for _ in range(ncolumns)]

    tokens = []
    while lines:
        line = lines.pop().strip()
        lowerline = line.lower()
        if (not line or
            line.startswith('_') or
            lowerline.startswith('data_') or

        if line.startswith('#'):

        line = line.split(' #')[0]

        if line.startswith(';'):
            moretokens = [parse_multiline_string(lines, line)]
            if ncolumns == 1:
                moretokens = [line]
                moretokens = shlex.split(line, posix=False)

        tokens += moretokens
        if len(tokens) < ncolumns:
        if len(tokens) == ncolumns:
            for i, token in enumerate(tokens):
            warnings.warn(f'Wrong number {len(tokens)} of tokens, '
                          f'expected {ncolumns}: {tokens}')

        # (Due to continue statements we cannot move this to start of loop)
        tokens = []

    if tokens:
        assert len(tokens) < ncolumns
        raise RuntimeError('CIF loop ended unexpectedly with incomplete row: '
                           f'{tokens}, expected {ncolumns} tokens')

    return columns

def parse_loop(lines: List[str]) -> Dict[str, List[CIFDataValue]]:
    """Parse a CIF loop. Returns a dict with column tag names as keys
    and a lists of the column content as values."""

    headers = list(parse_cif_loop_headers(lines))
    # Dict would be better.  But there can be repeated headers.

    columns = parse_cif_loop_data(lines, len(headers))

    columns_dict = {}
    for i, header in enumerate(headers):
        if header in columns_dict:
            warnings.warn(f'Duplicated loop tags: {header}')
            columns_dict[header] = columns[i]
    return columns_dict

def parse_items(lines: List[str], line: str) -> Dict[str, CIFData]:
    """Parse a CIF data items and return a dict with all tags."""
    tags: Dict[str, CIFData] = {}

    while True:
        if not lines:
        line = lines.pop().strip()
        if not line:
        lowerline = line.lower()
        if not line or line.startswith('#'):
        elif line.startswith('_'):
            key, value = parse_singletag(lines, line)
            tags[key.lower()] = value
        elif lowerline.startswith('loop_'):
        elif lowerline.startswith('data_'):
            if line:
        elif line.startswith(';'):
            parse_multiline_string(lines, line)
            raise ValueError(f'Unexpected CIF file entry: "{line}"')
    return tags

class NoStructureData(RuntimeError):

class CIFBlock(
    """A block (i.e., a single system) in a crystallographic information file.

    Use this object to query CIF tags or import information as ASE objects."""

    cell_tags = ['_cell_length_a', '_cell_length_b', '_cell_length_c',
                 '_cell_angle_alpha', '_cell_angle_beta', '_cell_angle_gamma']

    def __init__(self, name: str, tags: Dict[str, CIFData]): = name
        self._tags = tags

    def __repr__(self) -> str:
        tags = set(self._tags)
        return f'CIFBlock({}, tags={tags})'

    def __getitem__(self, key: str) -> CIFData:
        return self._tags[key]

    def __iter__(self) -> Iterator[str]:
        return iter(self._tags)

    def __len__(self) -> int:
        return len(self._tags)

    def get(self, key, default=None):
        return self._tags.get(key, default)

    def get_cellpar(self) -> Optional[List]:
            return [self[tag] for tag in self.cell_tags]
        except KeyError:
            return None

    def get_cell(self) -> Cell:
        cellpar = self.get_cellpar()
        if cellpar is None:
            return[0, 0, 0])

    def _raw_scaled_positions(self) -> Optional[np.ndarray]:
        coords = [self.get(name) for name in ['_atom_site_fract_x',
        # XXX Shall we try to handle mixed coordinates?
        # (Some scaled vs others fractional)
        if None in coords:
            return None
        return np.array(coords).T

    def _raw_positions(self) -> Optional[np.ndarray]:
        coords = [self.get('_atom_site_cartn_x'),
        if None in coords:
            return None
        return np.array(coords).T

    def _get_site_coordinates(self):
        scaled = self._raw_scaled_positions()

        if scaled is not None:
            return 'scaled', scaled

        cartesian = self._raw_positions()

        if cartesian is None:
            raise NoStructureData('No positions found in structure')

        return 'cartesian', cartesian

    def _get_symbols_with_deuterium(self):
        labels = self._get_any(['_atom_site_type_symbol',
        if labels is None:
            raise NoStructureData('No symbols')

        symbols = []
        for label in labels:
            if label == '.' or label == '?':
                raise NoStructureData('Symbols are undetermined')
            # Strip off additional labeling on chemical symbols
            match ='([A-Z][a-z]?)', label)
            symbol =
        return symbols

    def get_symbols(self) -> List[str]:
        symbols = self._get_symbols_with_deuterium()
        return [symbol if symbol != 'D' else 'H' for symbol in symbols]

    def _where_deuterium(self):
        return np.array([symbol == 'D' for symbol
                         in self._get_symbols_with_deuterium()], bool)

    def _get_masses(self) -> Optional[np.ndarray]:
        mask = self._where_deuterium()
        if not any(mask):
            return None

        symbols = self.get_symbols()
        masses = Atoms(symbols).get_masses()
        masses[mask] = 2.01355
        return masses

    def _get_any(self, names):
        for name in names:
            if name in self:
                return self[name]
        return None

    def _get_spacegroup_number(self):
        # Symmetry specification, see
        # for a
        # complete list of official keys.  In addition we also try to
        # support some commonly used depricated notations
        return self._get_any(['_space_group.it_number',

    def _get_spacegroup_name(self):
        hm_symbol = self._get_any(['_space_group_name_h-m_alt',

        hm_symbol = old_spacegroup_names.get(hm_symbol, hm_symbol)
        return hm_symbol

    def _get_sitesym(self):
        sitesym = self._get_any(['_space_group_symop_operation_xyz',
        if isinstance(sitesym, str):
            sitesym = [sitesym]
        return sitesym

    def _get_fractional_occupancies(self):
        return self.get('_atom_site_occupancy')

    def _get_setting(self) -> Optional[int]:
        setting_str = self.get('_symmetry_space_group_setting')
        if setting_str is None:
            return None

        setting = int(setting_str)
        if setting not in [1, 2]:
            raise ValueError(
                f'Spacegroup setting must be 1 or 2, not {setting}')
        return setting

    def get_spacegroup(self, subtrans_included) -> Spacegroup:
        # XXX The logic in this method needs serious cleaning up!
        no = self._get_spacegroup_number()
        if isinstance(no, str):
            # If the value was specified as "key  'value'" with ticks,
            # then "integer values" become strings and we'll have to
            # manually convert it:
            no = int(no)

        hm_symbol = self._get_spacegroup_name()
        sitesym = self._get_sitesym()

        if sitesym:
            # Special cases: sitesym can be None or an empty list.
            # The empty list could be replaced with just the identity
            # function, but it seems more correct to try to get the
            # spacegroup number and derive the symmetries for that.
            subtrans = [(0.0, 0.0, 0.0)] if subtrans_included else None

            spacegroup = spacegroup_from_data(
                no=no, symbol=hm_symbol, sitesym=sitesym,
                setting=1)  # should the setting be passed from somewhere?
        elif no is not None:
            spacegroup = no
        elif hm_symbol is not None:
            spacegroup = hm_symbol
            spacegroup = 1

        setting_std = self._get_setting()

        setting = 1
        setting_name = None
        if '_symmetry_space_group_setting' in self:
            assert setting_std is not None
            setting = setting_std
        elif '_space_group_crystal_system' in self:
            setting_name = self['_space_group_crystal_system']
        elif '_symmetry_cell_setting' in self:
            setting_name = self['_symmetry_cell_setting']

        if setting_name:
            no = Spacegroup(spacegroup).no
            if no in rhombohedral_spacegroups:
                if setting_name == 'hexagonal':
                    setting = 1
                elif setting_name in ('trigonal', 'rhombohedral'):
                    setting = 2
                        f'unexpected crystal system {setting_name!r} '
                        f'for space group {spacegroup!r}')
            # FIXME - check for more crystal systems...
                    f'crystal system {setting_name!r} is not '
                    f'interpreted for space group {spacegroup!r}. '
                    'This may result in wrong setting!')

        spg = Spacegroup(spacegroup, setting)
        if no is not None:
            assert int(spg) == no, (int(spg), no)
        return spg

    def get_unsymmetrized_structure(self) -> Atoms:
        """Return Atoms without symmetrizing coordinates.

        This returns a (normally) unphysical Atoms object
        corresponding only to those coordinates included
        in the CIF file, useful for e.g. debugging.

        This method may change behaviour in the future."""
        symbols = self.get_symbols()
        coordtype, coords = self._get_site_coordinates()

        atoms = Atoms(symbols=symbols,

        if coordtype == 'scaled':
            assert coordtype == 'cartesian'
            atoms.positions[:] = coords

        return atoms

    def has_structure(self):
        """Whether this CIF block has an atomic configuration."""
        except NoStructureData:
            return False
            return True

    def get_atoms(self, store_tags=False, primitive_cell=False,
                  subtrans_included=True, fractional_occupancies=True) -> Atoms:
        """Returns an Atoms object from a cif tags dictionary.  See read_cif()
        for a description of the arguments."""
        if primitive_cell and subtrans_included:
            raise RuntimeError(
                'Primitive cell cannot be determined when sublattice '
                'translations are included in the symmetry operations listed '
                'in the CIF file, i.e. when `subtrans_included` is True.')

        cell = self.get_cell()
        assert cell.rank in [0, 3]

        kwargs: Dict[str, Any] = {}
        if store_tags:
            kwargs['info'] = self._tags.copy()

        if fractional_occupancies:
            occupancies = self._get_fractional_occupancies()
            occupancies = None

        if occupancies is not None:
            # no warnings in this case
            kwargs['onduplicates'] = 'keep'

        # The unsymmetrized_structure is not the asymmetric unit
        # because the asymmetric unit should have (in general) a smaller cell,
        # whereas we have the full cell.
        unsymmetrized_structure = self.get_unsymmetrized_structure()

        if cell.rank == 3:
            spacegroup = self.get_spacegroup(subtrans_included)
            atoms = crystal(unsymmetrized_structure,
            atoms = unsymmetrized_structure
            if kwargs.get('info') is not None:
            if occupancies is not None:
                occ_dict = {
                    str(i): {sym: occupancies[i]}
                    for i, sym in enumerate(atoms.symbols)
      ['occupancy'] = occ_dict

        return atoms

def parse_block(lines: List[str], line: str) -> CIFBlock:
    assert line.lower().startswith('data_')
    blockname = line.split('_', 1)[1].rstrip()
    tags = parse_items(lines, line)
    return CIFBlock(blockname, tags)

def parse_cif(fileobj, reader='ase') -> Iterator[CIFBlock]:
    if reader == 'ase':
        return parse_cif_ase(fileobj)
    elif reader == 'pycodcif':
        return parse_cif_pycodcif(fileobj)
        raise ValueError(f'No such reader: {reader}')

def parse_cif_ase(fileobj) -> Iterator[CIFBlock]:
    """Parse a CIF file using ase CIF parser."""

    if isinstance(fileobj, str):
        with open(fileobj, 'rb') as fileobj:
            data =
        data =

    if isinstance(data, bytes):
        data = data.decode('latin1')
    data = format_unicode(data)
    lines = [e for e in data.split('\n') if len(e) > 0]
    if len(lines) > 0 and lines[0].rstrip() == '#\\#CIF_2.0':
        warnings.warn('CIF v2.0 file format detected; `ase` CIF reader might '
                      'incorrectly interpret some syntax constructions, use '
                      '`pycodcif` reader instead')
    lines = [''] + lines[::-1]    # all lines (reversed)

    while lines:
        line = lines.pop().strip()
        if not line or line.startswith('#'):

        yield parse_block(lines, line)

def parse_cif_pycodcif(fileobj) -> Iterator[CIFBlock]:
    """Parse a CIF file using pycodcif CIF parser."""
    if not isinstance(fileobj, str):
        fileobj =

        from pycodcif import parse
    except ImportError:
        raise ImportError(
            'parse_cif_pycodcif requires pycodcif ' +

    data, _, _ = parse(fileobj)

    for datablock in data:
        tags = datablock['values']
        for tag in tags.keys():
            values = [convert_value(x) for x in tags[tag]]
            if len(values) == 1:
                tags[tag] = values[0]
                tags[tag] = values
        yield CIFBlock(datablock['name'], tags)

def iread_cif(
    store_tags: bool = False,
    primitive_cell: bool = False,
    subtrans_included: bool = True,
    fractional_occupancies: bool = True,
    reader: str = 'ase',
) -> Iterator[Atoms]:
    # Find all CIF blocks with valid crystal data
    # TODO: return Atoms of the block name ``index`` if it is a string.
    images = []
    for block in parse_cif(fileobj, reader):
        if not block.has_structure():

        atoms = block.get_atoms(
            store_tags, primitive_cell,

    if index is None or index == ':':
        index = slice(None, None, None)

    if not isinstance(index, (slice, str)):
        index = slice(index, (index + 1) or None)

    for atoms in images[index]:
        yield atoms

[docs]def read_cif( fileobj, index=-1, *, store_tags: bool = False, primitive_cell: bool = False, subtrans_included: bool = True, fractional_occupancies: bool = True, reader: str = 'ase', ) -> Union[Atoms, List[Atoms]]: """Read Atoms object from CIF file. Parameters ---------- store_tags : bool If true, the *info* attribute of the returned Atoms object will be populated with all tags in the corresponding cif data block. primitive_cell : bool If true, the primitive cell is built instead of the conventional cell. subtrans_included : bool If true, sublattice translations are assumed to be included among the symmetry operations listed in the CIF file (seems to be the common behaviour of CIF files). Otherwise the sublattice translations are determined from setting 1 of the extracted space group. A result of setting this flag to true, is that it will not be possible to determine the primitive cell. fractional_occupancies : bool If true, the resulting atoms object will be tagged equipped with a dictionary `occupancy`. The keys of this dictionary will be integers converted to strings. The conversion to string is done in order to avoid troubles with JSON encoding/decoding of the dictionaries with non-string keys. Also, in case of mixed occupancies, the atom's chemical symbol will be that of the most dominant species. reader : str Select CIF reader. * ``ase`` : built-in CIF reader (default) * ``pycodcif`` : CIF reader based on ``pycodcif`` package Notes ----- Only blocks with valid crystal data will be included. """ g = iread_cif( fileobj, index, store_tags, primitive_cell, subtrans_included, fractional_occupancies, reader, ) if isinstance(index, (slice, str)): # Return list of atoms return list(g) else: # Return single atoms object return next(g)
def format_cell(cell: Cell) -> str: assert cell.rank == 3 lines = [] for name, value in zip(CIFBlock.cell_tags, cell.cellpar()): line = f'{name:20} {value}\n' lines.append(line) assert len(lines) == 6 return ''.join(lines) def format_generic_spacegroup_info() -> str: # We assume no symmetry whatsoever return '\n'.join([ '_space_group_name_H-M_alt "P 1"', '_space_group_IT_number 1', '', 'loop_', ' _space_group_symop_operation_xyz', " 'x, y, z'", '', ]) class CIFLoop: def __init__(self): self.names = [] self.formats = [] self.arrays = [] def add(self, name, array, fmt): assert name.startswith('_') self.names.append(name) self.formats.append(fmt) self.arrays.append(array) if len(self.arrays[0]) != len(self.arrays[-1]): raise ValueError(f'Loop data "{name}" has {len(array)} ' 'elements, expected {len(self.arrays[0])}') def tostring(self): lines = [] append = lines.append append('loop_') for name in self.names: append(f' {name}') template = ' ' + ' '.join(self.formats) ncolumns = len(self.arrays) nrows = len(self.arrays[0]) if ncolumns > 0 else 0 for row in range(nrows): arraydata = [array[row] for array in self.arrays] line = template.format(*arraydata) append(line) append('') return '\n'.join(lines)
[docs]@iofunction('wb') def write_cif(fd, images, cif_format=None, wrap=True, labels=None, loop_keys=None) -> None: r"""Write *images* to CIF file. wrap: bool Wrap atoms into unit cell. labels: list Use this list (shaped list[i_frame][i_atom] = string) for the '_atom_site_label' section instead of automatically generating it from the element symbol. loop_keys: dict Add the information from this dictionary to the `loop\_` section. Keys are printed to the `loop\_` section preceeded by ' _'. dict[key] should contain the data printed for each atom, so it needs to have the setup `dict[key][i_frame][i_atom] = string`. The strings are printed as they are, so take care of formating. Information can be re-read using the `store_tags` option of the cif reader. """ if cif_format is not None: warnings.warn('The cif_format argument is deprecated and may be ' 'removed in the future. Use loop_keys to customize ' 'data written in loop.', FutureWarning) if loop_keys is None: loop_keys = {} if hasattr(images, 'get_positions'): images = [images] fd = io.TextIOWrapper(fd, encoding='latin-1') try: for i, atoms in enumerate(images): blockname = f'data_image{i}\n' image_loop_keys = {key: loop_keys[key][i] for key in loop_keys} write_cif_image(blockname, atoms, fd, wrap=wrap, labels=None if labels is None else labels[i], loop_keys=image_loop_keys) finally: # Using the TextIOWrapper somehow causes the file to close # when this function returns. # Detach in order to circumvent this highly illogical problem: fd.detach()
def autolabel(symbols: Sequence[str]) -> List[str]: no: Dict[str, int] = {} labels = [] for symbol in symbols: if symbol in no: no[symbol] += 1 else: no[symbol] = 1 labels.append('%s%d' % (symbol, no[symbol])) return labels def chemical_formula_header(atoms): counts = atoms.symbols.formula.count() formula_sum = ' '.join(f'{sym}{count}' for sym, count in counts.items()) return (f'_chemical_formula_structural {atoms.symbols}\n' f'_chemical_formula_sum "{formula_sum}"\n') class BadOccupancies(ValueError): pass def expand_kinds(atoms, coords): # try to fetch occupancies // spacegroup_kinds - occupancy mapping symbols = list(atoms.symbols) coords = list(coords) occupancies = [1] * len(symbols) occ_info ='occupancy') kinds = atoms.arrays.get('spacegroup_kinds') if occ_info is not None and kinds is not None: for i, kind in enumerate(kinds): occ_info_kind = occ_info[str(kind)] symbol = symbols[i] if symbol not in occ_info_kind: raise BadOccupancies('Occupancies present but no occupancy ' 'info for "{symbol}"') occupancies[i] = occ_info_kind[symbol] # extend the positions array in case of mixed occupancy for sym, occ in occ_info[str(kind)].items(): if sym != symbols[i]: symbols.append(sym) coords.append(coords[i]) occupancies.append(occ) return symbols, coords, occupancies def atoms_to_loop_data(atoms, wrap, labels, loop_keys): if atoms.cell.rank == 3: coord_type = 'fract' coords = atoms.get_scaled_positions(wrap).tolist() else: coord_type = 'Cartn' coords = atoms.get_positions(wrap).tolist() try: symbols, coords, occupancies = expand_kinds(atoms, coords) except BadOccupancies as err: warnings.warn(str(err)) occupancies = [1] * len(atoms) symbols = list(atoms.symbols) if labels is None: labels = autolabel(symbols) coord_headers = [f'_atom_site_{coord_type}_{axisname}' for axisname in 'xyz'] loopdata = {} loopdata['_atom_site_label'] = (labels, '{:<8s}') loopdata['_atom_site_occupancy'] = (occupancies, '{:6.4f}') _coords = np.array(coords) for i, key in enumerate(coord_headers): loopdata[key] = (_coords[:, i], '{}') loopdata['_atom_site_type_symbol'] = (symbols, '{:<2s}') loopdata['_atom_site_symmetry_multiplicity'] = ( [1.0] * len(symbols), '{}') for key in loop_keys: # Should expand the loop_keys like we expand the occupancy stuff. # Otherwise user will never figure out how to do this. values = [loop_keys[key][i] for i in range(len(symbols))] loopdata['_' + key] = (values, '{}') return loopdata, coord_headers def write_cif_image(blockname, atoms, fd, *, wrap, labels, loop_keys): fd.write(blockname) fd.write(chemical_formula_header(atoms)) rank = atoms.cell.rank if rank == 3: fd.write(format_cell(atoms.cell)) fd.write('\n') fd.write(format_generic_spacegroup_info()) fd.write('\n') elif rank != 0: raise ValueError('CIF format can only represent systems with ' f'0 or 3 lattice vectors. Got {rank}.') loopdata, coord_headers = atoms_to_loop_data(atoms, wrap, labels, loop_keys) headers = [ '_atom_site_type_symbol', '_atom_site_label', '_atom_site_symmetry_multiplicity', *coord_headers, '_atom_site_occupancy', ] headers += ['_' + key for key in loop_keys] loop = CIFLoop() for header in headers: array, fmt = loopdata[header] loop.add(header, array, fmt) fd.write(loop.tostring())