cs551@mininet-vm:~/code$ ls
ryu_controller.py   start_mininet.py  topology.pyc  topology_bus.txt     topology_star.txt
ryu_controller.pyc  topology.py       topology.txt  topology_circle.txt

cs551@mininet-vm:~/code$ ryu-manager ryu_controller.py
loading app ryu_controller.py
Traceback (most recent call last):
  File "/usr/local/bin/ryu-manager", line 9, in <module>
    load_entry_point('ryu==4.32', 'console_scripts', 'ryu-manager')()
  File "/usr/local/lib/python2.7/dist-packages/ryu/cmd/manager.py", line 98, in main
    app_mgr.load_apps(app_lists)
  File "/usr/local/lib/python2.7/dist-packages/ryu/base/app_manager.py", line 415, in load_apps
    cls = self.load_app(app_cls_name)
  File "/usr/local/lib/python2.7/dist-packages/ryu/base/app_manager.py", line 392, in load_app
    mod = utils.import_module(name)
  File "/usr/local/lib/python2.7/dist-packages/ryu/utils.py", line 104, in import_module
    return importlib.import_module(modname)
  File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
ImportError: No module named ryu_controller.py

cs551@mininet-vm:~/code$ ryu-manager $pwd/ryu_controller.py
loading app /ryu_controller.py
Traceback (most recent call last):
  File "/usr/local/bin/ryu-manager", line 9, in <module>
    load_entry_point('ryu==4.32', 'console_scripts', 'ryu-manager')()
  File "/usr/local/lib/python2.7/dist-packages/ryu/cmd/manager.py", line 98, in main
    app_mgr.load_apps(app_lists)
  File "/usr/local/lib/python2.7/dist-packages/ryu/base/app_manager.py", line 415, in load_apps
    cls = self.load_app(app_cls_name)
  File "/usr/local/lib/python2.7/dist-packages/ryu/base/app_manager.py", line 392, in load_app
    mod = utils.import_module(name)
  File "/usr/local/lib/python2.7/dist-packages/ryu/utils.py", line 108, in import_module
    return importlib.import_module(modname)
  File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
ImportError: Import by filename is not supported.