import bpy
bevel_shapes = ["BezierCircle1","BezierCircle2","BezierCircle3","BezierCircle4","BezierCircle5"]
cuves = ["Circle 1","Circle 2","Circle 3","Circle 4","Circle 5"]
c = 0
for name in curves:
ob = bpy.data.objects.get(name)
if ob != None:
ob_bevel = bpy.data.objects.get(bevel_shapes[c])
if ob_bevel != None:
ob.data.bevel_object = ob_bevel
c += 1