Circular import

[jeffsilverm]

There is a circular import

ImportError while importing test module '/home/jeffs/python/nbmdt/test/test_utilities.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
test/test_utilities.py:12: in <module>
    import utilities
utilities.py:13: in <module>
    from nbmdt import SystemDescription
nbmdt.py:21: in <module>
    import datalink  # OSI layer 2: # Media Access Control: arp, ndp
datalink.py:14: in <module>ImportError while importing test module '/home/jeffs/python/nbmdt/test/test_utilities.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
test/test_utilities.py:12: in <module>
    import utilities
utilities.py:13: in <module>
    from nbmdt import SystemDescription
nbmdt.py:21: in <module>
    import datalink  # OSI layer 2: # Media Access Control: arp, ndp
datalink.py:14: in <module>
    from interface import Interface
interface.py:12: in <module>
    from utilities import OsCliInter, os_name, the_os
E   ImportError: cannot import name 'OsCliInter'

    from interface import Interface
interface.py:12: in <module>
    from utilities import OsCliInter, os_name, the_os
E   ImportError: cannot import name 'OsCliInter'

[jeffsilverm]

I think the problem is that utilities can't finish importing until it has nbmdt.SystemDecription. But nbmdt imports datalink and so on.

I think the solution is to move class SystemDescription into utilities.

jeffs@jeffs-desktop:/home/jeffs/python/nbmdt  (development) *  $ fgrep -n SystemDescription *.py */*.py
nbmdt.py:92:    current_system: utilities.SystemDescription = utilities.SystemDescription.discover()
nbmdt.py:134:    current_system = utilities.SystemDescription(mode=mode)
nbmdt.py:168:    nominal_system_description = utilities.SystemDescription ( configuration_file="nominal.txt" )
nbmdt.py:169:    current_system_description = utilities.SystemDescription ( )
utilities.py:13:from nbmdt import SystemDescription
utilities.py:40:class SystemDescription(object):
utilities.py:62:        a constructor, and all it does is create a SystemDescription object.
utilities.py:84:    def system_description_from_file(cls, filename: str) -> 'SystemDescription':
utilities.py:86:        Read a system description from a file and create a SystemDescription object.
utilities.py:87:        I couldn't figure out how to return a SystemDescription object, so I return an object
utilities.py:96:        return SystemDescription(
utilities.py:112:        :return: a SystemDescription object.
utilities.py:125:        my_system: object = SystemDescription(
utilities.py:215:            # nominal = SystemDescription.describe_current_state()
utilities.py:247:        nominal_system: SystemDescription = SystemDescription.system_description_from_file(filename)
utilities.py:256:class SystemDescriptionFile(SystemDescription):
utilities.py:262:        """Create a SystemDescription object which has all of the information in a system configuration file"""
utilities.py:266:        super(SystemDescriptionFile, self).__init__(applications=c_dict["applications"],
test/test_nbmdt.py:26:class testSystemDescription():
test/test_nbmdt.py:29:# Copy the rest of the methods from class SystemDescription in nbmdt.py to here
test/test_nbmdt.py:44:        a constructor, and all it does is create a SystemDescription object.
test/test_utilities.py:13:from nbmdt import SystemDescription
test/test_utilities.py:20:sd_obj = utilities.SystemDescriptionFile( TEST_CONFIGURATION_FILE )
test/test_utilities.py:21:assert isinstance( sd_obj, SystemDescription ), f"sd_obj is not an instance of SystemDescription, it's {type(sd_obj)}"
jeffs@jeffs-desktop:/home/jeffs/python/nbmdt  (development) *  $ 

[jeffsilverm]

There is another problem, this time with OsCliInter:

effs@jeffs-desktop:/home/jeffs/python/nbmdt  (development) *  $ python3 nbmdt.py
Testing the __file__ special variable: /home/jeffs/python/nbmdt/application.py
Traceback (most recent call last):
  File "nbmdt.py", line 16, in <module>
    import utilities
  File "/home/jeffs/python/nbmdt/utilities.py", line 13, in <module>
    from nbmdt import SystemDescription
  File "/home/jeffs/python/nbmdt/nbmdt.py", line 22, in <module>
    import datalink  # OSI layer 2: # Media Access Control: arp, ndp
  File "/home/jeffs/python/nbmdt/datalink.py", line 14, in <module>
    from interface import Interface
  File "/home/jeffs/python/nbmdt/interface.py", line 12, in <module>
    from utilities import OsCliInter, os_name, the_os
ImportError: cannot import name 'OsCliInter'
jeffs@jeffs-desktop:/home/jeffs/python/nbmdt  (development) *  $ 

jeffs@jeffs-desktop:/home/jeffs/python/nbmdt  (development) *  $ fgrep OsCliInter *.py */*.py
application.py:            apps_str: str = utilities.OsCliInter.run_command(["ps", "-ax"])
datalink.py:from utilities import OsCliInter, os_name, the_os
datalink.py:            datalinks_str: str = OsCliInter.run_command(cls.DISCOVER_ALL_DATALINKS_COMMAND)
datalink.py:            raise NotImplemented(f"{OsCliInter.system} is not implemented yet in DataLink")
guts_of_interface.py:        lnk_str: str = OsCliInter.run_command(PhysicalLink.DISCOVER_LINK_COMMAND)
guts_of_interface.py:            raise NotImplemented(f"{OsCliInter.system} is not implemented yet in PhysicalLink")
guts_of_interface.py:            raise NotImplementedError(f"In DataLink.discover, {OsCliInter.system} is not implemented")
guts_of_interface.py:        lnk_str:str = OsCliInter.run_command(cls.DISCOVER_ADDR_COMMAND )
interface.py:from utilities import OsCliInter, os_name, the_os
interface.py:        results = OsCliInter.run_command([Interface.IP_COMMAND, "link", "list"])
physical.py:        results = utilities.OsCliInter.run_command(command=command)
physical.py:        if "linux" == utilities.OsCliInter.system:
physical.py:        elif "windows" == utilities.OsCliInter.system:
physical.py:        elif 'darwin' == utilities.OsCliInter.system:
physical.py:        elif 'java' == utilities.OsCliInter.system:
physical.py:    results_xml:str = utilities.OsCliInter.run_command(command=command)
utilities.py:class OsCliInter(object):
utilities.py:    # Since the system is going to be the same across the entire program, populate it when the OsCliInter object is
utilities.py:    # imported for the first time and then make it available to any object in class OsCliInter (which should not need
utilities.py:# of class OsCliInter or else the compiler will raise a NameError exception at compile time
utilities.py:os_name: str = OsCliInter.system.lower()
utilities.py:        print(f"In linux, the uname -a command output is \n{OsCliInter.run_command(['uname', '-a'])}\n.")
test/test_interface.py:@patch("utilities.OsCliInter.run_command")
test/test_interface.py:@patch("utilities.OsCliInter.run_command")
test/test_interface.py:@patch("utilities.OsCliInter.run_command")
test/test_interface.py:@patch("utilities.OsCliInter.run_command")
test/test_interface.py:@patch("utilities.OsCliInter.run_command")
jeffs@jeffs-desktop:/home/jeffs/python/nbmdt  (development) *  $ 

Resolve Issue 29 before proceeding.

[jeffsilverm]

The easy way to test this is to have utilities.py run by itself.

    jeffs@evil-kali:~/nbmdt$ python3 utilities.py 
    Enter an issue that I changed the values of the constants from integers to strings for reliability
    Traceback (most recent call last):
      File "utilities.py", line 14, in <module>
        import application
      File "/home/jeffs/nbmdt/application.py", line 20, in <module>
        import utilities
      File "/home/jeffs/nbmdt/utilities.py", line 16, in <module>
        import datalink
      File "/home/jeffs/nbmdt/datalink.py", line 15, in <module>
        from utilities import OsCliInter, os_name, the_os
    ImportError: cannot import name 'OsCliInter' from 'utilities' (/home/jeffs/nbmdt/utilities.py)
    jeffs@evil-kali:~/nbmdt$ 

Why is this happening?

jeffs@evil-kali:~/nbmdt$ fgrep OsCliInter utilities.py 
class OsCliInter(object):
# Since the system is going to be the same across the entire program, populate it when the OsCliInter object is
# imported for the first time and then make it available to any object in class OsCliInter (which should not need
# of class OsCliInter or else the compiler will raise a NameError exception at compile time
os_name: str = OsCliInter.system.lower()
        print(f"In linux, the uname -a command output is \n{OsCliInter.run_command(['uname', '-a'])}\n.")
jeffs@evil-kali:~/nbmdt$ 

Figure out to import an inner class