Example #1
0
    def __init__(self, pwinput):
        """
        Parse inputs's namelist and cards to create attributes of the info.

        :param pwinput:
            Any one of the following

                * A string of the (existing) absolute path to the pwinput file.
                * A single string containing the pwinput file's text.
                * A list of strings, with the lines of the file as the elements.
                * A file object. (It will be opened, if it isn't already.)

        :raises IOError: if ``pwinput`` is a file and there is a problem reading
            the file.
        :raises TypeError: if ``pwinput`` is a list containing any non-string
            element(s).
        :raises aiida.common.exceptions.ParsingError: if there are issues
            parsing the pwinput.
        """
        # Get the text of the pwinput file as a single string.
        # File.
        if isinstance(pwinput, file_types):
            try:
                self.input_txt = pwinput.read()
            except IOError:
                raise IOError('Unable to open the provided pwinput, {}'
                              ''.format(file.name))
        # List.
        elif isinstance(pwinput, list):
            if all(isinstance(s, basestring) for s in pwinput):
                self.input_txt = ''.join(pwinput)
            else:
                raise TypeError(
                    'You provided a list to parse, but some elements were not '
                    'strings. Each element should be a string containing a line'
                    'of the pwinput file.')
        # Path or string of the text.
        elif isinstance(pwinput, basestring):
            if os.path.isfile(pwinput):
                if os.path.isabs(pwinput):
                    with open(pwinput) as f:
                        self.input_txt = f.read()
                else:
                    raise IOError(
                        'Please provide the absolute path to an existing '
                        'pwinput file.')
            else:
                self.input_txt = pwinput
        else:
            raise TypeError("Unknown type for input 'pwinput': {}".format(
                type(pwinput)))

        # Check that pwinput is not empty.
        if len(self.input_txt.strip()) == 0:
            raise ParsingError('The pwinput provided was empty!')
Example #2
0
    def str01_to_bool(s):
        """
        Map strings '0', '1' strings to bools: '0' --> True; '1' --> False.

        While this is opposite to the QE standard, this mapping is what needs to
        be passed to aiida in a 'settings' ParameterData object.
        (See the _if_pos method of BasePwCpInputGenerator)
        """
        if s == '0':
            return True
        elif s == '1':
            return False
        else:
            raise ParsingError(
                'Unable to convert if_pos = "{}" to bool'.format(s))
Example #3
0
def parse_k_points(txt):
    """
    Return a dictionary containing info from the K_POINTS card block in txt.

    .. note:: If the type of kpoints (where type = x in the card header,
           "K_POINTS x") is not present, type will be returned as 'tpiba', the
           QE default.

    :param txt: A single string containing the QE input text to be parsed.

    :returns:
        A dictionary containing

            * type: the type of kpoints (always lower-case)
            * points: an Nx3 list of the kpoints (will not be present if type =
              'gamma' or type = 'automatic')
            * weights: a 1xN list of the kpoint weights (will not be present if
              type = 'gamma' or type = 'automatic')
            * mesh: a 1x3 list of the number of equally-spaced points in each
              direction of the Brillouin zone, as in Monkhorst-Pack grids (only
              present if type = 'automatic')
            * offset: a 1x3 list of the grid offsets in each direction of the
              Brillouin zone (only present if type = 'automatic')
              (**Note:** The offset value for each direction will be *one of*
              ``0.0`` [no offset] *or* ``0.5`` [offset by half a grid step].
              This differs from the Quantum Espresso convention, where an offset
              value of ``1`` corresponds to a half-grid-step offset, but adheres
              to the current AiiDa convention.


        Examples::

            {'type': 'crystal',
             'points': [[0.125,  0.125,  0.0],
                        [0.125,  0.375,  0.0],
                        [0.375,  0.375,  0.0]],
             'weights': [1.0, 2.0, 1.0]}

            {'type': 'automatic',
             'points': [8, 8, 8],
             'offset': [0.0, 0.5, 0.0]}

            {'type': 'gamma'}

    :raises aiida.common.exceptions.ParsingError: if there are issues
        parsing the input.
    """
    # Define re for the special-type card block.
    k_points_special_block_re = re.compile(
        r"""
        ^ [ \t]* K_POINTS [ \t]*
            [{(]? [ \t]* (?P<type>\S+?)? [ \t]* [)}]? [ \t]* $\n
        ^ [ \t]* \S+ [ \t]* $\n  # nks
        (?P<block>
         (?:
          ^ [ \t]* \S+ [ \t]+ \S+ [ \t]+ \S+ [ \t]+ \S+ [ \t]* $\n?
         )+
        )
        """, RE_FLAGS)
    # Define re for the info contained in the special-type block.
    k_points_special_re = re.compile(
        r"""
    ^ [ \t]* (\S+) [ \t]+ (\S+) [ \t]+ (\S+) [ \t]+ (\S+) [ \t]* $\n?
    """, RE_FLAGS)
    # Define re for the automatic-type card block and its line of info.
    k_points_automatic_block_re = re.compile(
        r"""
        ^ [ \t]* K_POINTS [ \t]* [{(]? [ \t]* automatic [ \t]* [)}]? [ \t]* $\n
        ^ [ \t]* (\S+) [ \t]+ (\S+) [ \t]+ (\S+) [ \t]+ (\S+) [ \t]+ (\S+)
            [ \t]+ (\S+) [ \t]* $\n?
        """, RE_FLAGS)
    # Define re for the gamma-type card block. (There is no block info.)
    k_points_gamma_block_re = re.compile(
        r"""
        ^ [ \t]* K_POINTS [ \t]* [{(]? [ \t]* gamma [ \t]* [)}]? [ \t]* $\n
        """, RE_FLAGS)
    # Try finding the card block using all three types.
    info_dict = {}
    match = k_points_special_block_re.search(txt)
    if match:
        if match.group('type') is not None:
            info_dict['type'] = match.group('type').lower()
        else:
            info_dict['type'] = 'tpiba'
        blockstr = match.group('block')
        points = []
        weights = []
        for match in k_points_special_re.finditer(blockstr):
            points.append(list(map(float, match.group(1, 2, 3))))
            weights.append(float(match.group(4)))
        info_dict['points'] = points
        info_dict['weights'] = weights
    else:
        match = k_points_automatic_block_re.search(txt)
        if match:
            info_dict['type'] = 'automatic'
            info_dict['points'] = list(map(int, match.group(1, 2, 3)))
            info_dict['offset'] = [
                0. if x == 0 else 0.5 for x in map(int, match.group(4, 5, 6))
            ]
        else:
            match = k_points_gamma_block_re.search(txt)
            if match:
                info_dict['type'] = 'gamma'
            else:
                raise ParsingError('K_POINTS card not found in\n' + txt)
    return info_dict
Example #4
0
def parse_atomic_species(txt):
    """
    Return a dictionary containing info from the ATOMIC_SPECIES card block
    in txt.

    :param txt: A single string containing the QE input text to be parsed.
    :type txt: str

    :returns:
        A dictionary with

            * names: list of the atom names (e.g. 'Si', 'Si0', 'Si_0') (case
              as-is)
            * masses: list of the masses of the atoms in 'names'
            * pseudo_file_names: list of the pseudopotential file names for the
              atoms in 'names' (case as-is)

        Example::

            {'names': ['Li', 'O', 'Al', 'Si'],
             'masses': [6.941,  15.9994, 26.98154, 28.0855],
             'pseudo_file_names': ['Li.pbe-sl-rrkjus_psl.1.0.0.UPF',
                                   'O.pbe-nl-rrkjus_psl.1.0.0.UPF',
                                   'Al.pbe-nl-rrkjus_psl.1.0.0.UPF',
                                   'Si.pbe-nl-rrkjus_psl.1.0.0.UPF']

    :raises aiida.common.exceptions.ParsingError: if there are issues
        parsing the input.
    """
    # Define re for atomic species card block.
    atomic_species_block_re = re.compile(
        r"""
        ^ [ \t]* ATOMIC_SPECIES [ \t]* $\n
        (?P<block>
         (?:
          ^ [ \t]* \S+ [ \t]+ \S+ [ \t]+ \S+ [ \t]* $\n?
         )+
        )
        """, RE_FLAGS)
    # Define re for the info contained in the block.
    atomic_species_re = re.compile(
        r"""
        ^ [ \t]* (?P<name>\S+) [ \t]+ (?P<mass>\S+) [ \t]+ (?P<pseudo>\S+)
            [ \t]* $\n?
        """, RE_FLAGS)
    # Find the card block and extract units and the lines of the block.
    try:
        match = atomic_species_block_re.search(txt)
    except AttributeError:
        raise ParsingError('The ATOMIC_SPECIES card block was not found in\n' +
                           txt)
    # Make sure the card block lines were extracted. If they were, store the
    # string of lines as blockstr.
    if match.group('block') is None:
        raise ParsingError(
            'The ATOMIC_POSITIONS card block was parse as empty in\n' + txt)
    else:
        blockstr = match.group('block')
    # Define a small helper function to convert strings of fortran-type floats.
    fortfloat = lambda s: float(s.replace('d', 'e').replace('D', 'E'))
    # Now, extract the name, mass, and pseudopotential file name from each line
    # of the card block.
    names, masses, pseudo_fnms = [], [], []
    for match in atomic_species_re.finditer(blockstr):
        names.append(match.group('name'))
        masses.append(fortfloat(match.group('mass')))
        pseudo_fnms.append(match.group('pseudo'))
    info_dict = dict(names=names, masses=masses, pseudo_file_names=pseudo_fnms)
    return info_dict
Example #5
0
def parse_cell_parameters(txt):
    """
    Return dict containing info from the CELL_PARAMETERS card block in txt.

    .. note:: This card is only needed if ibrav = 0. Therefore, if the card is
           not present, the function will return None and not raise an error.

    .. note:: If the units are unspecified, they will be returned as None. The
           units interpreted by QE depend on whether or not one of 'celldm(1)'
           or 'a' is set in &SYSTEM.

    :param txt: A single string containing the QE input text to be parsed.

    :returns:
        A dictionary (if CELL_PARAMETERS is present; else: None) with

            * units: the units of the lattice vectors (always lower-case) or
              None
            * cell: 3x3 list with lattice vectors as rows

        For example::

            {'units': 'angstrom',
             'cell': [[16.9, 0.0, 0.0],
                      [-2.6, 8.0, 0.0],
                      [-2.6, -3.5, 7.2]]}

    :raises aiida.common.exceptions.ParsingError: if there are issues
        parsing the input.
    """
    # Define re for the card block.
    cell_parameters_block_re = re.compile(
        r"""
        ^ [ \t]*
        CELL_PARAMETERS [ \t]*
        [{(]? \s* (?P<units>[a-z]*) \s* [)}]? \s* [\n]
        (?P<block>
        (
            (
                \s*             # White space in front of the element spec is ok
                (
                    # First number
                    (
                        [-|+]?   # Plus or minus in front of the number (optional)
                        (\d*     # optional decimal in the beginning .0001 is ok, for example
                        [\.]     # There has to be a dot followed by
                        \d+)     # at least one decimal
                        |        # OR
                        (\d+     # at least one decimal, followed by
                        [\.]?    # an optional dot
                        \d*)     # followed by optional decimals
                        ([E|e|d|D][+|-]?\d+)?  # optional exponents E+03, e-05, d0, D0
                    
                        (
                            \s+      # White space between numbers
                            [-|+]?   # Plus or minus in front of the number (optional)
                            (\d*     # optional decimal in the beginning .0001 is ok, for example
                            [\.]     # There has to be a dot followed by
                            \d+)     # at least one decimal
                            |        # OR
                            (\d+     # at least one decimal, followed by
                            [\.]?    # an optional dot
                            \d*)     # followed by optional decimals
                            ([E|e|d|D][+|-]?\d+)?  # optional exponents E+03, e-05, d0, D0
                        ){2}         # I expect three float values
                    )
                    |
                    \#
                    |
                    !            # If a line is commented out, that is also ok
                )
                .*               # I do not care what is after the comment or the vector
                |                # OR
                \s*              # A line only containing white space
             )
            [\n]                 # line break at the end
        ){3}                     # I need exactly 3 vectors
    )
    """, RE_FLAGS)

    cell_vector_regex = re.compile(
        r"""
        ^                        # Linestart
        [ \t]*                   # Optional white space
        (?P<x>                   # Get x
            [\-|\+]? ( \d*[\.]\d+ | \d+[\.]?\d*)
            ([E|e|d|D][+|-]?\d+)?
        )
        [ \t]+
        (?P<y>                   # Get y
            [\-|\+]? (\d*[\.]\d+ | \d+[\.]?\d*)
            ([E|e|d|D][+|-]?\d+)?
        )
        [ \t]+
        (?P<z>                   # Get z
            [\-|\+]? (\d*[\.]\d+ | \d+[\.]?\d*)
            ([E|e|d|D][+|-]?\d+)?
        )
        """, re.X | re.M)
    #~ cell_parameters_block_re = re.compile(r"""
    #~ ^ [ \t]* CELL_PARAMETERS [ \t]*
    #~ [{(]? [ \t]* (?P<units>\S+?)? [ \t]* [)}]? [ \t]* $\n
    #~ (?P<block>
    #~ (?:
    #~ ^ [ \t]* \S+ [ \t]+ \S+ [ \t]+ \S+ [ \t]* $\n?
    #~ ){3}
    #~ )
    #~ """, RE_FLAGS)
    # Define re for the info contained in the block.
    #~ atomic_species_re = re.compile(r"""
    #~ ^ [ \t]* (\S+) [ \t]+ (\S+) [ \t]+ (\S+) [ \t]* $\n?
    #~ """, RE_FLAGS)
    # Find the card block and extract units and the lines of the block.
    match = cell_parameters_block_re.search(txt)
    if not match:
        return None
    # Use specified units or None if not specified.
    units = match.group('units')
    if units is not None:
        units = units.lower()
    # Get the string containing the lines of the block.
    if match.group('block') is None:
        raise ParsingError(
            'The CELL_PARAMETER card block was parsed as empty in\n' + txt)
    else:
        blockstr = match.group('block')
    # Define a small helper function to convert strings of fortran-type floats.
    fortfloat = lambda s: float(s.replace('d', 'e').replace('D', 'E'))
    # Now, extract the lattice vectors.
    lattice_vectors = []
    for match in cell_vector_regex.finditer(blockstr):
        lattice_vectors.append(
            list(
                map(fortfloat,
                    (match.group('x'), match.group('y'), match.group('z')))))
    info_dict = dict(units=units, cell=lattice_vectors)
    return info_dict
Example #6
0
def parse_atomic_positions(txt):
    """
    Return a dictionary containing info from the ATOMIC_POSITIONS card block
    in txt.

    .. note:: If the units are unspecified, they will be returned as None.

    :param txt: A single string containing the QE input text to be parsed.
    :type txt: str

    :returns:
        A dictionary with

            * units: the units of the positions (always lower-case) or None
            * names: list of the atom names (e.g. ``'Si'``, ``'Si0'``,
              ``'Si_0'``)
            * positions: list of the [x, y, z] positions
            * fixed_coords: list of [x, y, z] (bools) of the force modifications
              (**Note:** True <--> Fixed, as defined in the
              ``BasePwCpInputGenerator._if_pos`` method)

        For example::

            {'units': 'bohr',
             'names': ['C', 'O'],
             'positions': [[0.0, 0.0, 0.0],
                           [0.0, 0.0, 2.5]]
             'fixed_coords': [[False, False, False],
                              [True, True, True]]}


    :raises aiida.common.exceptions.ParsingError: if there are issues
        parsing the input.
    """
    def str01_to_bool(s):
        """
        Map strings '0', '1' strings to bools: '0' --> True; '1' --> False.

        While this is opposite to the QE standard, this mapping is what needs to
        be passed to aiida in a 'settings' ParameterData object.
        (See the _if_pos method of BasePwCpInputGenerator)
        """
        if s == '0':
            return True
        elif s == '1':
            return False
        else:
            raise ParsingError(
                'Unable to convert if_pos = "{}" to bool'.format(s))

    # Define re for the card block.
    # NOTE: This will match card block lines w/ or w/out force modifications.
    atomic_positions_block_re = re.compile(
        r"""
        ^ \s* ATOMIC_POSITIONS \s*                      # Atomic positions start with that string
        [{(]? \s* (?P<units>\S+?)? \s* [)}]? \s* $\n    # The units are after the string in optional brackets
        (?P<block>                                  # This is the block of positions
            (
                (
                    \s*                                 # White space in front of the element spec is ok
                    (
                        [A-Za-z]+[A-Za-z0-9]{0,2}       # Element spec
                        (
                            \s+                         # White space in front of the number
                            [-|+]?                      # Plus or minus in front of the number (optional)
                            (
                                (
                                    \d*                 # optional decimal in the beginning .0001 is ok, for example
                                    [\.]                # There has to be a dot followed by
                                    \d+                 # at least one decimal
                                )
                                |                       # OR
                                (
                                    \d+                 # at least one decimal, followed by
                                    [\.]?               # an optional dot ( both 1 and 1. are fine)
                                    \d*                 # And optional number of decimals (1.00001)
                                )                        # followed by optional decimals
                            )
                            ([E|e|d|D][+|-]?\d+)?       # optional exponents E+03, e-05
                        ){3}                            # I expect three float values
                        ((\s+[0-1]){3}\s*)?             # Followed by optional ifpos
                        \s*                             # Followed by optional white space
                        |
                        \#.*                            # If a line is commented out, that is also ok
                        |
                        \!.*                            # Comments also with excl. mark in fortran
                    )
                    |                                   # OR
                    \s*                                 # A line only containing white space
                 )
                [\n]                                    # line break at the end
            )+                                          # A positions block should be one or more lines
        )
        """, re.X | re.M)

    atomic_positions_block_re_ = re.compile(
        r"""
        ^ [ \t]* ATOMIC_POSITIONS [ \t]*
            [{(]? [ \t]* (?P<units>\S+?)? [ \t]* [)}]? [ \t]* $\n
        (?P<block>
         (?:
          ^ [ \t]*
          (?:
           \S+ [ \t]+ \S+ [ \t]+ \S+ [ \t]+ \S+
           (?:[ \t]+ [{(]? [ \t]* [01] [ \t]+ [01] [ \t]+ [01] [ \t]* [)}]?)?
          )
          [ \t]* $\n?
         )+
        )
        """, RE_FLAGS)
    # Define re for atomic positions without force modifications.

    atomic_positions_w_constraints_re = re.compile(
        r"""
        ^                                       # Linestart
        [ \t]*                                  # Optional white space
        (?P<name>[A-Za-z]+[A-Za-z0-9]{0,2})\s+   # get the symbol, max 3 chars, starting with a char
        (?P<x>                                  # Get x
            [\-|\+]?(\d*[\.]\d+ | \d+[\.]?\d*)
            ([E|e|d|D][+|-]?\d+)?
        )
        [ \t]+
        (?P<y>                                  # Get y
            [\-|\+]?(\d*[\.]\d+ | \d+[\.]?\d*)
            ([E|e|d|D][+|-]?\d+)?
        )
        [ \t]+
        (?P<z>                                  # Get z
            [\-|\+]?(\d*[\.]\d+ | \d+[\.]?\d*)
            ([E|e|d|D][+|-]?\d+)?
        )
        [ \t]*
        (?P<fx>[01]?)                           # Get fx
        [ \t]*
        (?P<fy>[01]?)                           # Get fx
        [ \t]*
        (?P<fz>[01]?)                           # Get fx
        """, re.X | re.M)
    # Find the card block and extract units and the lines of the block.
    match = atomic_positions_block_re.search(txt)
    if not match:
        raise ParsingError(
            'The ATOMIC_POSITIONS card block was not found in\n' + txt)
    # Get the units. If they are not found, match.group('units') will be None.
    units = match.group('units')
    if units is not None:
        units = units.lower()
    # Get the string containing the lines of the block.
    if match.group('block') is None:
        raise ParsingError(
            'The ATOMIC_POSITIONS card block was parsed as empty in\n' + txt)
    else:
        blockstr = match.group('block')

    # Define a small helper function to convert if_pos strings to bools that
    # correspond to the mapping of BasePwCpInputGenerator._if_pos method.

    # Define a small helper function to convert strings of fortran-type floats.
    fortfloat = lambda s: float(s.replace('d', 'e').replace('D', 'E'))
    # Parse the lines of the card block, extracting an atom name, position
    # and fixed coordinates.
    names, positions, fixed_coords = [], [], []
    # First, try using the re for lines without force modifications. Set the
    # default force modification to the default (True) for each atom.
    # PROBLEM this changes the order of the atoms, which is unwanted!
    #~ for match in atomic_positions_re.finditer(blockstr):
    #~ names.append(match.group('name'))
    #~ positions.append(map(fortfloat, match.group('x', 'y', 'z')))
    #~ fixed_coords.append(3 * [False])  # False <--> not fixed (the default)
    # Next, try using the re for lines with force modifications.
    for match in atomic_positions_w_constraints_re.finditer(blockstr):
        positions.append(list(map(fortfloat, match.group('x', 'y', 'z'))))
        fixed_coords_this_pos = [
            f or '1' for f in match.group('fx', 'fy', 'fz')
        ]  # False <--> not fixed (the default)
        fixed_coords.append(list(map(str01_to_bool, fixed_coords_this_pos)))
        names.append(match.group('name'))

    # Check that the number of atomic positions parsed is equal to the number of
    # lines in blockstr
    # LK removed this check since lines can be commented out, and that is fine.
    # n_lines = len(blockstr.rstrip().split('\n'))
    #~ if len(names) != n_lines:
    #~ raise ParsingError(
    #~ 'Only {} atomic positions were parsed from the {} lines of the '
    #~ 'ATOMIC_POSITIONS card block:\n{}'.format(len(names), n_lines,
    #~ blockstr)
    #~ )
    info_dict = dict(units=units,
                     names=names,
                     positions=positions,
                     fixed_coords=fixed_coords)
    return info_dict
Example #7
0
def parse_namelists(txt):
    """
    Parse txt to extract a dictionary of the namelist info.
    
    :param txt: A single string containing the QE input text to be parsed.
    :type txt: str

    :returns:
        A nested dictionary of the namelists and their key-value pairs. The
        namelists will always be upper-case keys, while the parameter keys will
        always be lower-case.

        For example::

            {"CONTROL": {"calculation": "bands",
                         "prefix": "al",
                         "pseudo_dir": "./pseudo",
                         "outdir": "./out"},
             "ELECTRONS": {"diagonalization": "cg"},
             "SYSTEM": {"nbnd": 8,
                        "ecutwfc": 15.0,
                        "celldm(1)": 7.5,
                        "ibrav": 2,
                        "nat": 1,
                        "ntyp": 1}
            }

    :raises aiida.common.exceptions.ParsingError: if there are issues
        parsing the input.
    """
    # TODO: Incorporate support for algebraic expressions?
    # Define the re to match a namelist and extract the info from it.
    namelist_re = re.compile(
        r"""
        ^ [ \t]* &(\S+) [ \t]* $\n  # match line w/ nmlst tag; save nmlst name
        (
         [\S\s]*?                # match any line non-greedily
        )                        # save the group of text between nmlst
        ^ [ \t]* / [ \t]* $\n    # match line w/ "/" as only non-whitespace char
        """, re.M | re.X)
    # Define the re to match and extract all of the key = val pairs inside
    # a block of namelist text.
    key_value_re = re.compile(
        r"""
        [ \t]* (\S+?) [ \t]*  # match and store key
        =               # equals sign separates key and value
        [ \t]* (\S+?) [ \t]*  # match and store value
        [\n,]           # return or comma separates "key = value" pairs
        """, re.M | re.X)
    # Scan through the namelists...
    params_dict = {}
    for nmlst, blockstr in namelist_re.findall(txt):
        # ...extract the key value pairs, storing them each in nmlst_dict,...
        nmlst_dict = {}
        for key, valstr in key_value_re.findall(blockstr):
            nmlst_dict[key.lower()] = str2val(valstr)
        # ...and, store nmlst_dict as a value in params_dict with the namelist
        # as the key.
        if len(nmlst_dict.keys()) > 0:
            params_dict[nmlst.upper()] = nmlst_dict
    if len(params_dict) == 0:
        raise ParsingError(
            'No data was found while parsing the namelist in the following '
            'text\n' + txt)
    # TODO: uppercase correct
    return params_dict
Example #8
0
    def __init__(self, pwinput):
        """
        Parse inputs's namelist and cards to create attributes of the info.

        :param pwinput:
            Any one of the following

                * A string of the (existing) absolute path to the pwinput file.
                * A single string containing the pwinput file's text.
                * A list of strings, with the lines of the file as the elements.
                * A file object. (It will be opened, if it isn't already.)

        :raises IOError: if ``pwinput`` is a file and there is a problem reading
            the file.
        :raises TypeError: if ``pwinput`` is a list containing any non-string
            element(s).
        :raises qe_tools.utils.exceptions.ParsingError: if there are issues
            parsing the pwinput.
        """
        # Get the text of the pwinput file as a single string.
        # File.
        if isinstance(pwinput, file_types):
            try:
                self.input_txt = pwinput.read()
            except IOError:
                raise IOError('Unable to open the provided pwinput, {}'
                              ''.format(file.name))
        # List.
        elif isinstance(pwinput, list):
            if all(isinstance(s, basestring) for s in pwinput):
                self.input_txt = ''.join(pwinput)
            else:
                raise TypeError(
                    'You provided a list to parse, but some elements were not '
                    'strings. Each element should be a string containing a line'
                    'of the pwinput file.')
        # Path or string of the text.
        elif isinstance(pwinput, basestring):
            if os.path.isfile(pwinput):
                if os.path.isabs(pwinput):
                    with open(pwinput) as f:
                        self.input_txt = f.read()
                else:
                    raise IOError(
                        'Please provide the absolute path to an existing '
                        'pwinput file.')
            else:
                self.input_txt = pwinput
        else:
            raise TypeError("Unknown type for input 'pwinput': {}".format(
                type(pwinput)))

        # Check that pwinput is not empty.
        if len(self.input_txt.strip()) == 0:
            raise ParsingError('The pwinput provided was empty!')

        # Take care explicitly of Windows newlines: \r\n
        # (open would do it automatically, but if the uses passes a string
        # this would not be done properly)
        self.input_txt = self.input_txt.replace('\r\n', '\n')
        # This is instead for Mac <=9 (hopefully nobody still uses it, but
        # who knows) that just used \r
        self.input_txt = self.input_txt.replace('\r', '\n')
        # Add a newline, as a partial fix to #15
        self.input_txt += "\n"