[Python-Dev] Syntax suggestion for imports

[Jeroen Ruigrok van der Werven]

-On [20080103 08:53], Raymond Hettinger (python at rcn.com) wrote:
>Thanks.  I'm more curious about the content of those lines.  Does the 
>proposed syntax help, does the need go away in Py3.0, what is the typical 
>pattern?

These are some of the examples, I've tried to reduce them to specific use
patterns:

To determine if some feature is available:
try:
    pygments = __import__('pygments', {}, {}, [])
    have_pygments = True
except ImportError:
    have_pygments = False

try:
    from docutils import nodes
    from docutils.core import publish_parts
    from docutils.parsers import rst
    from docutils import __version__
except ImportError:
    raise TracError(_('Docutils not found'))
if StrictVersion(__version__) < StrictVersion('0.3.9'):
    raise TracError(_('Docutils version >= %(version)s required, '
                      '%(found)s found', version='0.3.9', found=__version__))

To specify which specific version we have of a given module:
try:
    import pysqlite2.dbapi2 as sqlite
    have_pysqlite = 2
except ImportError:
    try:
        import sqlite3 as sqlite
        have_pysqlite = 2
    except ImportError:
        try:
            import sqlite
            have_pysqlite = 1
        except ImportError:
            have_pysqlite = 0

This gets repeated a lot in order to see if we have threading:
try:
    import threading
except ImportError:
    import dummy_threading as threading
    threading._get_ident = lambda: 0

Functions we do use and need, fall-back to support code if not present:
try:
    from operator import attrgetter, itemgetter
except ImportError:
    def attrgetter(name):
        def _getattr(obj):
            return getattr(obj, name)
        return _getattr
    def itemgetter(name):
        def _getitem(obj):
            return obj[name]
        return _getitem

Masking functions if a particular function is not found:
try:
    from base64 import b64decode
except ImportError:
    from base64 import decodestring as b64decode

-- 
Jeroen Ruigrok van der Werven <asmodai(-at-)in-nomine.org> / asmodai
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