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"""This preprocessor detect cells using a different language through
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magic extensions such as `%%R` or `%%octave`. Cell's metadata is marked
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so that the appropriate highlighter can be used in the `highlight`
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filter.
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"""
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# Copyright (c) IPython Development Team.
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# Distributed under the terms of the Modified BSD License.
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from __future__ import print_function, absolute_import
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import re
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# Our own imports
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from .base import Preprocessor
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from IPython.utils.traitlets import Dict
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class HighlightMagicsPreprocessor(Preprocessor):
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"""
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Detects and tags code cells that use a different languages than Python.
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"""
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# list of magic language extensions and their associated pygment lexers
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default_languages = Dict(
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default_value={
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'%%R': 'r',
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'%%bash': 'bash',
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'%%cython': 'cython',
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'%%javascript': 'javascript',
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'%%julia': 'julia',
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'%%latex': 'latex',
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'%%octave': 'octave',
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'%%perl': 'perl',
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'%%ruby': 'ruby',
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'%%sh': 'sh'})
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# user defined language extensions
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languages = Dict(
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config=True,
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help=("Syntax highlighting for magic's extension languages. "
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"Each item associates a language magic extension such as %%R, "
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"with a pygments lexer such as r."))
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def __init__(self, config=None, **kw):
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"""Public constructor"""
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super(HighlightMagicsPreprocessor, self).__init__(config=config, **kw)
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# Update the default languages dict with the user configured ones
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self.default_languages.update(self.languages)
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# build a regular expression to catch language extensions and choose
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# an adequate pygments lexer
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any_language = "|".join(self.default_languages.keys())
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self.re_magic_language = re.compile(
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r'^\s*({0})\s+'.format(any_language))
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def which_magic_language(self, source):
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"""
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When a cell uses another language through a magic extension,
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the other language is returned.
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If no language magic is detected, this function returns None.
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Parameters
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----------
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source: str
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Source code of the cell to highlight
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"""
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m = self.re_magic_language.match(source)
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if m:
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# By construction of the re, the matched language must be in the
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# languages dictionary
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return self.default_languages[m.group(1)]
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else:
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return None
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def preprocess_cell(self, cell, resources, cell_index):
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"""
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Tags cells using a magic extension language
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Parameters
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----------
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cell : NotebookNode cell
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Notebook cell being processed
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resources : dictionary
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Additional resources used in the conversion process. Allows
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preprocessors to pass variables into the Jinja engine.
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cell_index : int
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Index of the cell being processed (see base.py)
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"""
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# Only tag code cells
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if cell.cell_type == "code":
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magic_language = self.which_magic_language(cell.source)
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if magic_language:
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cell['metadata']['magics_language'] = magic_language
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return cell, resources
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