Metadata-Version: 2.1
Name: pysmiles
Version: 1.0.1
Summary: A lightweight SMILES reader and writer
Home-page: https://github.com/pckroon/pysmiles
Author: P C Kroon
Author-email: p.c.kroon@rug.nl
License: Apache 2.0
Description: [![Build Status](https://travis-ci.org/pckroon/pysmiles.svg?branch=master)](https://travis-ci.org/pckroon/pysmiles)
        [![Coverage Status](https://coveralls.io/repos/github/pckroon/pysmiles/badge.svg?branch=master)](https://coveralls.io/github/pckroon/pysmiles?branch=master)
        
        # pysmiles: The lightweight and pure-python SMILES reader and writer
        
        This is a small project I started because I couldn't find any SMILES reader or
        writer that was easy to install (read: Python only). Currently, the writer is
        extremely basic, and although it should produce valid SMILES they won't be
        pretty. The reader is in a better state, and should be usable.
        
        SMILES strings are assumed to be as specified by the
        [OpenSmiles standard][opensmiles].
        
        ## Molecules
        Molecules are depicted as [Networkx][networkx] graphs. Atoms are the nodes of
        the graph, and bonds are the edges. Nodes can have the following attributes:
        - element: str. This describes the element of the atom. Defaults to '\*'
            meaning unknown.
        - aromatic: bool. Whether the atom is part of an (anti)-aromatic system. 
            Defaults to False.
        - isotope: float. The mass of the atom. Defaults to unknown.
        - hcount: int. The number of implicit hydrogens attached to this atom.
            Defaults to 0.
        - charge: int. The charge of this atom. Defaults to 0.
        - class: int. The "class" of this atom. Defaults to 0.
        
        Edges have the following attributes:
        - order: Number. The bond order. 1.5 is used for aromatic bonds. Defaults to 1.
        
        There is currently no way of specifying stereo chemical information, and this
        is discarded upon reading. Somewhere in the future this will probably be
        stored in the "stereo" attribute of nodes.
        
        ## Reading SMILES
        The function `read_smiles(smiles, explicit_hydrogen=False,
        zero_order_bonds=True, reinterpret_aromatic=True)` can be used to parse a
        SMILES string. It should not be used to validate whether a string is a valid
        SMILES string --- the function does very little validation whether your SMILES string makes chemical sense.
        Edges in the created molecule will always have an 'order'
        attribute. Nodes will have the relevant attributes in so far they are
        specified. Atoms for which the element is not known (\*) will not have an
        element attribute.
        - `explicit_hydrogen` determines whether hydrogen atoms should be
            represented as explicit nodes in the created molecule, or implicit in the
            'hcount' attribute.
        - `zero_order_bonds` determines whether zero-order bonds (.) in the SMILES
            string should result in edges in the produced molecule.
        - `reinterpret_aromatic` determines whether aromaticity should be 
            reinterpreted, and determined from the constructed molecule, or whether
            the aromaticity specifications from the SMILES string (lower case 
            elements) should be taken as leading. If `True`, will also set bond orders 
            to 1 for bonds that are not part of an aromatic ring and have a bond order 
            of 1.5. If `False`, will create a molecule using *only* the information in 
            the SMILES string.
        
        ### Stereochemical information
        Currently the library cannot handle stereochemical information, neither E/Z nor
        R/S. Any stereochemical information that was in the SMILES string will be
        *discarded* upon parsing. This means there will be no difference between
        parsing *e.g.* `N[C@](Br)(O)C`, `N[C@@](Br)(O)C` and `NC(Br)(O)C`. Parsing
        these *will result in the same molecule*. The same holds for *e.g.* `F/C=C/F`
        and `FC=CF`. These will result in the same molecule.
        
        Whenever stereochemical information is being discarded a warning will be
        logged using the built-in `logging` module. If you want to disable all the
        messages logged by `pysmiles` you can add the following snippet to your code,
        without interfering with any logging by your own code:
        
        ```python
        import logging
        logging.getLogger('pysmiles').setLevel(logging.CRITICAL)  # Anything higher than warning
        ```
        
        
        ## Writing SMILES
        The function `write_smiles(molecule, default_element='*', start=None)` can be
        used to write SMILES strings from a molecule. The function does *not* check 
        whether your molecule makes chemical sense. Instead, it writes a SMILES 
        representation of the molecule you provided, and nothing else.
        - `default_element` is the element to use for nodes that do not have an 
            'element' attribute.
        - `start` is the key of the node where the depth first traversal should be 
            started. Something clever is done if not specified.
        
        ## Additional functions
        In addition to these two core functions, four more functions are exposed that
        can help in creating chemically relevant molecules with minimal work.
        
        - `fill_valence(mol, respect_hcount=True, respect_bond_order=True,
                         max_bond_order=3)`
            This function will fill the valence of all atoms in your molecule by 
            incrementing the 'hcount' and, if specified, bond orders. Note that it does
            not use 'charge' attribute to find the correct valence.
            - `repect_hcount`: bool. Whether existing hcounts can be overwritten.
            - `respect_bond_order`: bool. Whether bond orders can be changed
            - `max_bond_order`: int. The maximum bond order that will be set.
        - `add_explicit_hydrogens(mol)`
            This function transforms implicit hydrogens, specified by 'hcount' 
            attributes, to explicit nodes.
        - `remove_explicit_hydrogens(mol)`
            This function does the inverse of `add_explicit_hydrogens`: it will remove
            explicit hydrogen nodes and add them to the relevant 'hcount' attributes.
        - `correct_aromatic_rings(mol)`
            This function marks all (anti)-aromatic atoms in your molecule, and sets 
            all bonds between (anti)-aromatic atoms to order 1.5.
            It fills the valence of all atoms (see also `fill_valence`) before trying
            to figure our which atoms are aromatic. It works by first finding all 
            atoms that are in a ring. Next, for every atom in every ring it is checked
            whether the atoms are sp2 hybridized (note that this is a vague term. 
            Strictly speaking we check whether their element is something that *could*
            be aromatic, and whether they have 2 or 3 bonds.). Finally, the number of 
            electrons per ring is counted, and if this is even, the atoms in the ring
            are said to be aromatic.
            This function is the most fragile in the whole library, and I expect it to
            produce wrong answers in some cases. In particular for fused (aromatic)
            ring systems (such as indole) and rings with extracyclic heteroatoms
            (O=C1C=CC=C1). Buyer beware.
        
        ## Examples
        ### Reading
        ```python
        from pysmiles import read_smiles
        
        smiles = 'C1CC[13CH2]CC1C1CCCCC1'
        mol = read_smiles(smiles)
        
        print(mol.nodes(data='element'))
        # [(0, 'C'),
        #  (1, 'C'),
        #  (2, 'C'),
        #  (3, 'C'),
        #  (4, 'C'),
        #  (5, 'C'),
        #  (6, 'C'),
        #  (7, 'C'),
        #  (8, 'C'),
        #  (9, 'C'),
        #  (10, 'C'),
        #  (11, 'C')]
        print(mol.nodes(data='hcount'))
        # [(0, 2),
        #  (1, 2),
        #  (2, 2),
        #  (3, 2),
        #  (4, 2),
        #  (5, 1),
        #  (6, 1),
        #  (7, 2),
        #  (8, 2),
        #  (9, 2),
        #  (10, 2),
        #  (11, 2)]
        
        mol_with_H = read_smiles(smiles, explicit_hydrogen=True)
        print(mol_with_H.nodes(data='element'))
        # [(0, 'C'),
        #  (1, 'C'),
        #  (2, 'C'),
        #  (3, 'C'),
        #  (4, 'C'),
        #  (5, 'C'),
        #  (6, 'C'),
        #  (7, 'C'),
        #  (8, 'C'),
        #  (9, 'C'),
        #  (10, 'C'),
        #  (11, 'C'),
        #  (12, 'H'),
        #  (13, 'H'),
        #  (14, 'H'),
        #  (15, 'H'),
        #  (16, 'H'),
        #  (17, 'H'),
        #  (18, 'H'),
        #  (19, 'H'),
        #  (20, 'H'),
        #  (21, 'H'),
        #  (22, 'H'),
        #  (23, 'H'),
        #  (24, 'H'),
        #  (25, 'H'),
        #  (26, 'H'),
        #  (27, 'H'),
        #  (28, 'H'),
        #  (29, 'H'),
        #  (30, 'H'),
        #  (31, 'H'),
        #  (32, 'H'),
        # (33, 'H')]
        ```
        
        ### Writing
        ```python
        import networkx as nx
        from pysmiles import write_smiles, fill_valence
        
        mol = nx.Graph()
        mol.add_edges_from([(0, 1), (1, 2), (1, 3), (3, 4), (1, 5), (3, 6)])
        for idx, ele in enumerate('CCCCOCO'):
            mol.nodes[idx]['element'] = ele
        mol.nodes[4]['charge'] = -1
        mol.nodes[4]['hcount'] = 0
        mol.edges[3, 6]['order'] = 2
        
        print(write_smiles(mol))
        # [O-]C(=O)C([C])([C])[C]
        fill_valence(mol, respect_hcount=True)
        print(write_smiles(mol))
        # [O-]C(=O)C(C)(C)C
        ```
        
        ## Limitations
        - The writer produces non-recommended SMILES strings (as per OpenSmiles).
        - `fill_valence` does not use 'charge' to find the correct valence.
        - `correct_aromatic_rings` is fragile.
        - There is currently no way of specifying stereo chemical information. The 
            parser can deal with it, but it will be discarded.
        - It only processes SMILES. This might later be extended to e.g. InChi, SLN,
            SMARTS, etc.
        
        ## Requirements
        - [networkx][networkx]
        
        ## Similar projects
        There are more python projects that deal with SMILES, and I try to list at 
        least some of them here. If yours is missing, feel free to open up a PR.
        - [PySMILE](https://github.com/jhosmer/PySmile): A similar named project, 
            capable of encoding/decoding SMILE format objects. Doesn't deal with 
            SMILES.
        - [RDKit](https://github.com/rdkit/rdkit): A collection of cheminformatics and 
            machine-learning software, capable of reading and writing SMILES, InChi, 
            and others.
        - [OpenEye Chem toolkit](https://www.eyesopen.com/oechem-tk): The OpenEye 
            chemistry toolkit is a programming library for chemistry and 
            cheminformatics. It is capable of dealing with (canonical) SMILES and 
            InChi.
        
        ## License
        PySmiles is distributed under the Apache 2.0 license.
            Copyright 2018 Peter C Kroon
        
            Licensed under the Apache License, Version 2.0 (the "License");
            you may not use this file except in compliance with the License.
            You may obtain a copy of the License at
        
                http://www.apache.org/licenses/LICENSE-2.0
        
            Unless required by applicable law or agreed to in writing, software
            distributed under the License is distributed on an "AS IS" BASIS,
            WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
            See the License for the specific language governing permissions and
            limitations under the License.
        
        
        [opensmiles]: http://opensmiles.org/
        [networkx]: https://networkx.github.io/
        
        
Keywords: SMILES cheminformatics chemistry
Platform: UNKNOWN
Classifier: Development Status :: 4 - Beta
Classifier: Intended Audience :: Developers
Classifier: Intended Audience :: Science/Research
Classifier: License :: OSI Approved :: Apache Software License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python :: 3
Classifier: Topic :: Scientific/Engineering :: Bio-Informatics
Classifier: Topic :: Scientific/Engineering :: Chemistry
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