sage.combinat: Modularization fixes

Author: Matthias Koeppe

src/sage/combinat/species/generating_series.py

@@ -53,11 +53,12 @@
 from sage.rings.lazy_series_ring import LazyPowerSeriesRing, LazySymmetricFunctions
 from sage.rings.integer import Integer
 from sage.rings.rational_field import QQ
-from sage.arith.misc import divisors
+from sage.arith.misc import divisors, factorial
 from sage.combinat.partition import Partition, Partitions
-from sage.combinat.sf.sf import SymmetricFunctions
 from sage.misc.cachefunc import cached_function
-from sage.arith.misc import factorial
+from sage.misc.lazy_import import lazy_import
+
+lazy_import('sage.combinat.sf.sf', 'SymmetricFunctions')
 
 
 class OrdinaryGeneratingSeries(LazyPowerSeries):

src/sage/combinat/species/misc.py

@@ -17,13 +17,15 @@
 #                  http://www.gnu.org/licenses/
 #*****************************************************************************
 
-from sage.groups.perm_gps.permgroup import PermutationGroup
-from sage.groups.perm_gps.permgroup import PermutationGroup_generic
-from sage.groups.perm_gps.constructor import PermutationGroupElement
-from sage.groups.perm_gps.permgroup_named import SymmetricGroup
-from sage.misc.misc_c import prod
 from functools import wraps
 
+from sage.misc.misc_c import prod
+from sage.misc.lazy_import import lazy_import
+
+lazy_import('sage.groups.perm_gps.permgroup', ['PermutationGroup', 'PermutationGroup_generic'])
+lazy_import('sage.groups.perm_gps.constructor', 'PermutationGroupElement')
+lazy_import('sage.groups.perm_gps.permgroup_named', 'SymmetricGroup')
+
 
 def change_support(perm, support, change_perm=None):
     """