Only load required I/O functions at the last minute

astrofrog · astrofrog · commit dcaf1a6ac35d · 2014-11-08T09:41:14.000+01:00
diff --git a/astropy/io/ascii/connect.py b/astropy/io/ascii/connect.py
@@ -20,15 +20,11 @@ def read_asciitable(filename, **kwargs):
     from .ui import read
     return read(filename, **kwargs)
 
-io_registry.register_reader('ascii', Table, read_asciitable)
-
 
 def write_asciitable(table, filename, **kwargs):
     from .ui import write
     return write(table, filename, **kwargs)
 
-io_registry.register_writer('ascii', Table, write_asciitable)
-
 
 def io_read(format, filename, **kwargs):
     from .ui import read
@@ -44,27 +40,3 @@ def io_write(format, table, filename, **kwargs):
 
 def io_identify(suffix, origin, filepath, fileobj, *args, **kwargs):
     return filepath is not None and filepath.endswith(suffix)
-
-
-def _get_connectors_table():
-    from .core import FORMAT_CLASSES
-
-    rows = []
-    rows.append(('ascii', '', 'Yes', 'ASCII table in any supported format (uses guessing)'))
-    for format in sorted(FORMAT_CLASSES):
-        cls = FORMAT_CLASSES[format]
-
-        io_format = 'ascii.' + cls._format_name
-        description = getattr(cls, '_description', '')
-        class_link = ':class:`~{}.{}`'.format(cls.__module__, cls.__name__)
-        suffix = getattr(cls, '_io_registry_suffix', '')
-        can_write = 'Yes' if getattr(cls, '_io_registry_can_write', True) else ''
-
-        rows.append((io_format, suffix, can_write,
-                     '{}: {}'.format(class_link, description)))
-    out = Table(list(zip(*rows)), names=('Format', 'Suffix', 'Write', 'Description'))
-    for colname in ('Format', 'Description'):
-        width = max(len(x) for x in out[colname])
-        out[colname].format = '%-{}s'.format(width)
-
-    return out
diff --git a/astropy/io/fits/connect.py b/astropy/io/fits/connect.py
@@ -292,7 +292,3 @@ def write_table_fits(input, output, overwrite=False):
 
     # Write out file
     table_hdu.writeto(output)
-
-io_registry.register_reader('fits', Table, read_table_fits)
-io_registry.register_writer('fits', Table, write_table_fits)
-io_registry.register_identifier('fits', Table, is_fits)
diff --git a/astropy/io/misc/connect.py b/astropy/io/misc/connect.py
@@ -8,8 +8,4 @@
 from .hdf5 import read_table_hdf5, write_table_hdf5, is_hdf5
 
 from .. import registry as io_registry
-from ...table import Table
-
-io_registry.register_reader('hdf5', Table, read_table_hdf5)
-io_registry.register_writer('hdf5', Table, write_table_hdf5)
-io_registry.register_identifier('hdf5', Table, is_hdf5)
+from ...table import Table
diff --git a/astropy/io/registry.py b/astropy/io/registry.py
@@ -19,11 +19,54 @@
 
 __doctest_skip__ = ['register_identifier']
 
-
+_builtin_registered = False
 _readers = OrderedDict()
 _writers = OrderedDict()
 _identifiers = OrderedDict()
 
+# Add built-in readers/writers to the registry manually, and refer to the
+# functions by strings to avoid importing those modules.
+def _register_builtins():
+
+    global _builtin_registered
+
+    if not _builtin_registered:
+
+        from ..table import Table
+
+        _builtin_registered = True
+
+        # FITS
+        register_reader("fits", Table, 'astropy.io.fits.connect.read_table_fits')
+        register_writer("fits", Table, 'astropy.io.fits.connect.write_table_fits')
+        register_identifier("fits", Table, 'astropy.io.fits.connect.is_fits')
+
+        # VOTABLE
+        register_reader('votable', Table, 'astropy.io.votable.connect.read_table_votable')
+        register_writer('votable', Table, 'astropy.io.votable.connect.write_table_votable')
+        register_identifier('votable', Table, 'astropy.io.votable.connect.is_votable')
+
+        # HDF5
+        register_reader('hdf5', Table, 'astropy.io.misc.hdf5.read_table_hdf5')
+        register_writer('hdf5', Table, 'astropy.io.misc.hdf5.write_table_hdf5')
+        register_identifier('hdf5', Table, 'astropy.io.misc.hdf5.is_hdf5')
+
+        # JSViewer
+        register_writer('jsviewer', Table, 'astropy.table.jsviewer.write_table_jsviewer')
+
+        # ASCII
+        register_reader('ascii', Table, 'astropy.io.ascii.connect.read_asciitable')
+        register_writer('ascii', Table, 'astropy.io.ascii.connect.write_asciitable')
+
+        # Remaining ASCII formats - for now can only import io.ascii to force
+        # meta-classes to register.
+        from . import ascii
+
+def _get_function_by_string(path_to_function):
+    import importlib
+    module, function = path_to_function.rsplit('.', 1)
+    return getattr(importlib.import_module(module), function)
+
 
 def get_formats(data_class=None):
     """
@@ -39,6 +82,9 @@ def get_formats(data_class=None):
     format_table: Table
         Table of available I/O formats
     """
+
+    _register_builtins()
+
     from ..table import Table
     format_classes = sorted(set(_readers) | set(_writers),
                             key=lambda tup: tup[0])
@@ -242,11 +288,16 @@ def register_identifier(data_format, data_class, identifier, force=False):
 
 
 def identify_format(origin, data_class_required, path, fileobj, args, kwargs):
+    _register_builtins()
     # Loop through identifiers to see which formats match
     valid_formats = []
     for data_format, data_class in _identifiers:
         if _is_best_match(data_class_required, data_class, _identifiers):
-            if _identifiers[(data_format, data_class)](
+            identifier = _identifiers[(data_format, data_class)]
+            if isinstance(identifier, six.string_types):
+                identifier = _get_function_by_string(identifier)
+                _identifiers[(data_format, data_class)] = identifier
+            if identifier(
                 origin, path, fileobj, *args, **kwargs):
                 valid_formats.append(data_format)
 
@@ -264,11 +315,16 @@ def _get_format_table_str(data_class, readwrite):
 
 
 def get_reader(data_format, data_class):
+    _register_builtins()
     # Get all the readers that work for `data_format`
     readers = [(fmt, cls) for fmt, cls in _readers if fmt == data_format]
     for reader_format, reader_class in readers:
         if _is_best_match(data_class, reader_class, readers):
-            return _readers[(reader_format, reader_class)]
+            reader = _readers[(reader_format, reader_class)]
+            if isinstance(reader, six.string_types):
+                reader = _get_function_by_string(reader)
+                _readers[(reader_format, reader_class)] = reader
+            return reader
     else:
         format_table_str = _get_format_table_str(data_class, 'Read')
         raise Exception("No reader defined for format '{0}' and class '{1}'.\n"
@@ -278,10 +334,15 @@ def get_reader(data_format, data_class):
 
 
 def get_writer(data_format, data_class):
+    _register_builtins()
     writers = [(fmt, cls) for fmt, cls in _writers if fmt == data_format]
     for writer_format, writer_class in writers:
         if _is_best_match(data_class, writer_class, writers):
-            return _writers[(writer_format, writer_class)]
+            writer = _writers[(writer_format, writer_class)]
+            if isinstance(writer, six.string_types):
+                writer = _get_function_by_string(writer)
+                _writers[(writer_format, writer_class)] = writer
+            return writer
     else:
         format_table_str = _get_format_table_str(data_class, 'Write')
         raise Exception("No writer defined for format '{0}' and class '{1}'.\n"
diff --git a/astropy/io/votable/connect.py b/astropy/io/votable/connect.py
@@ -151,8 +151,3 @@ def write_table_votable(input, output, table_id=None, overwrite=False,
 
     # Write out file
     table_file.to_xml(output, tabledata_format=tabledata_format)
-
-
-io_registry.register_reader('votable', Table, read_table_votable)
-io_registry.register_writer('votable', Table, write_table_votable)
-io_registry.register_identifier('votable', Table, is_votable)
diff --git a/astropy/table/__init__.py b/astropy/table/__init__.py
@@ -24,9 +24,3 @@ class Conf(_config.ConfigNamespace):
 from .np_utils import TableMergeError
 from .operations import join, hstack, vstack
 
-# Import routines that connect readers/writers to astropy.table
-from ..io.ascii import connect
-from ..io.fits import connect
-from ..io.misc import connect
-from ..io.votable import connect
-from . import jsviewer
diff --git a/astropy/table/jsviewer.py b/astropy/table/jsviewer.py
@@ -172,5 +172,3 @@ def write_table_jsviewer(table, filename, table_id=None,
     htmldict['js'] =  jsv.html_js(table_id=table_id)
 
     table.write(filename, format='html', htmldict=htmldict)
-
-io_registry.register_writer('jsviewer', Table, write_table_jsviewer)
