libs/dmigrations/migration_loader.py

   1 from migrations import BaseMigration
   2 from exceptions import *
   3
   4 import imp
   5 import os
   6
   7 def load_migration_from_path(file_path, dev=False):
   8     """
   9     Given a file_path to a 001_blah.py file, returns the migration object
  10     contained in that file. The file should have a "migration" symbol which
  11     is an instance of a BaseMigration subclass. Raise an error otherwise.
  12     """
  13     dir_name, file_name = os.path.split(file_path)
  14
  15     mod_name = file_name.replace('.py', '')
  16     dot_py_suffix = ('.py', 'U', 1) # From imp.get_suffixes()[2]
  17
  18     mod = imp.load_module(mod_name, open(file_path), file_path, dot_py_suffix)
  19
  20     try:
  21         migration = mod.migration
  22     except AttributeError:
  23         raise BadMigrationError(
  24             u'Module %s has no migration instance' % file_path
  25         )
  26
  27     if not isinstance(migration, BaseMigration):
  28         raise BadMigrationError(
  29             u'Migration %s is not a BaseMigration subclass' % file_path
  30         )
  31
  32     # Set up .filepath and .name based on where it was loaded from
  33     migration.filepath = file_path
  34     migration.name = mod_name
  35     migration.dev = dev
  36
  37     return migration