Develop Reference

How can I tell pyreverse to include classes within modules within packages?

I have this folder structure:
.
└── src
├── a
│   ├── __init__.py
│   ├── a.py
│   └── b.py
└── main.py
Contents of a/a.py:
class A:
def __init__(self):
self.name = 'a'
Contents of a/b.py
from a.a import A
class B(A):
def __init__(self):
self.name = 'b'
Conents of main.py:
from a.a import A
from a.b import B
print(A().name)
print(B().name)
As you can see, class B inherits from class A
I have confirmed that the program works as expected, so there are no errors in the code
I wish to run something along the lines of: pyreverse src/**/* -o png and generate a UML diagram showing me that class B inherits from class A (I have a bigger project with many more directories, hence the reason for the **/* part).
However, what I am getting at the moment is this:
The expected would be something like this:

Answering my own question: the answer was to simply cd to src/, or do this:
export PYTHONPATH="${PYTHONPATH}:${PWD}/src"

Python's importlib and inspect for static class members

In a long-running app I need to dynamically modify static class members based on path to the class' module and the class name.
Ex. I have a class pack1.mod1.Person and by definition I know it has a age property. So utilizing the importlib and inspect I try to load the class using the module path and class name and update the age property. It all seems fine until I read the the age property from my naturally imported Person class and find it's not updated.
Here are some more details:
.
├── app.py
└── pack1
├── __init__.py
└── mod1.py
mod1.py
class Person:
age = 42
app.py
import inspect
import os
from importlib import util
from pack1.mod1 import Person
if __name__ == '__main__':
Person.age = 3
print(Person.age) # => 3
spec = util.spec_from_file_location('pack1.mod1', os.path.join('pack1', 'mod1.py'))
module = util.module_from_spec(spec)
spec.loader.exec_module(module)
members = inspect.getmembers(module)
for x, member in inspect.getmembers(module, lambda i: inspect.isclass(i) and i.__name__ == Person.__name__):
print('Person:', Person.age) # => Person: 3
print('Person from inspect:', member.age) # => Person from inspect: 42
Person.age = 11
member.age = 66
print('Person:', Person.age) # => Person: 11
print('Person from inspect:', member.age) # => Person from inspect: 66
In the app.py I would expect member and Person to be the same thing but as the example shows they aren't.
What am I missing and how to achieve such an update on the static members of a class?

Python has no way of knowing that the regularly imported module and the manually module are "the same": Using util.spec_from_file_location up to spec.loader.exec_module side-steps Python's module registry and explicitly creates a new instance of the module.
Instead, use the native operations of the interpreter (import, ...) or their programmatic equivalents (importlib.load_module, ...)
If the module/class are well-known, one can import it regularly and directly inspect it.
import pack1.mod1
pack1.mod1.Person.age = 66
If module and class are only known by name, one can look them up from the existing modules.
import importlib
module_name, qualname, attribute, value = 'pack1.mod1', 'Person', 'age', 66
obj = importlib.import_module(module_name) # same as `import {module_name}`
for part in qualname.split('.'):
obj = getattr(obj, part) # same as `{obj}.{part}
setattr(obj, attribute, value) # same as `{obj}.{attribute} = {value}`

Python metaClass and import *

Main Goal: Automatically register classes (by a string) in a factory to be created dynamically at run time using that string, classes can be in their own file and not grouped in one file.
I have couple of classes which all inherit from the same base class and they define a string as their type.
A user wants to get an instance of one of these classes but only knows the type at run time.
Therefore I have a factory to create an instance given a type.
I didn't want to hard code an "if then statements" so I have a meta class to register all the sub classes of the base class:
class MetaRegister(type):
# we use __init__ rather than __new__ here because we want
# to modify attributes of the class *after* they have been
# created
def __init__(cls, name, bases, dct):
if not hasattr(cls, 'registry'):
# this is the base class. Create an empty registry
cls.registry = {}
else:
# this is a derived class. Add cls to the registry
interface_id = cls().get_model_type()
cls.registry[interface_id] = cls
super(MetaRegister, cls).__init__(name, bases, dct)
The problem is that for this to work the factory has to import all the subclass (So the meta class runs).
To fix this you can use from X import *
But for this to work you need to define an __all__ var in the __init__.py file of the package to include all the sub classes.
I don't want to hard code the sub classes because it beats the purpose of using the meta class.
I can go over the file in the package using:
import glob
from os.path import dirname, basename, isfile
modules = glob.glob(dirname(__file__) + "/*.py")
__all__ = [basename(f)[:-3] for f in modules if isfile(f)]
Which works great, but the project needs to compile to a single .so file, which nullifies the use of the file system.
So how could I achieve my main goal of creating instances at run time without hard codding the type?
Is there a way to populate an __all__ var at run time without touching the filesystem?
In Java I'd probably decorate the class with an annotation and then get all the classes with that annotation at run time, is there something similar on python?
I know there are decorators in python but I'm not sure I can use them in this way.
Edit 1:
Each subclass must be in a file:
- Models
-- __init__.py
-- ModelFactory.py
-- Regression
--- __init__.py
--- Base.py
--- Subclass1.py
--- Subclass2ExtendsSubclass1.py
Edit 2: Some code to Illustrate the problem:
+ main.py
|__ Models
|__ __init__.py
|__ ModelFactory.py
|__ Regression
|__ init__.py
|__ Base.py
|__ SubClass.py
|__ ModelRegister.py
main.py
from models.ModelFactory import ModelFactory
if __name__ == '__main__':
ModelFactory()
ModelFactory.py
from models.regression.Base import registry
import models.regression
class ModelFactory(object):
def get(self, some_type):
return registry[some_type]
ModelRegister.py
class ModelRegister(type):
# we use __init__ rather than __new__ here because we want
# to modify attributes of the class *after* they have been
# created
def __init__(cls, name, bases, dct):
print cls.__name__
if not hasattr(cls, 'registry'):
# this is the base class. Create an empty registry
cls.registry = {}
else:
# this is a derived class. Add cls to the registry
interface_id = cls().get_model_type()
cls.registry[interface_id] = cls
super(ModelRegister, cls).__init__(name, bases, dct)
Base.py
from models.regression.ModelRegister import ModelRegister
class Base(object):
__metaclass__ = ModelRegister
def get_type(self):
return "BASE"
SubClass.py
from models.regression.Base import Base
class SubClass(Base):
def get_type(self):
return "SUB_CLASS"
Running it you can see only "Base" it printed.
Using a decorator gives the same results.

A simple way to register classes as runtime is to use decorators:
registry = {}
def register(cls):
registry[cls.__name__] = cls
return cls
#register
class Foo(object):
pass
#register
class Bar(object):
pass
This will work if all of your classes are defined in the same module, and if that module is imported at runtime. Your situation, however, complicates things. First, you want to define your classes in different modules. This means that we must be able to dynamically determine which modules exist within our package at runtime. This would be straightforward using Python's pkgutil module, however, you also state that you are using Nuitka to compile your package into an extension module. pkgutil doesn't work with such extension modules.
I cannot find any documented way of determining the modules contained within an Nuitka extension module from within Python. If one does exist, the decorator approach above would work after dynamically importing each submodule.
As it is, I believe the most straightforward solution is to write a script to generate an __init__.py before compiling. Suppose we have the following package structure:
.
├── __init__.py
├── plugins
│   ├── alpha.py
│   └── beta.py
└── register.py
The "plugins" are contained within the plugins directory. The contents of the files are:
# register.py
# -----------
registry = {}
def register(cls):
registry[cls.__name__] = cls
return cls
# __init__.py
# -----------
from . import plugins
from . import register
# ./plugins/alpha.py
# ------------------
from ..register import register
#register
class Alpha(object):
pass
# ./plugins/beta.py
# ------------------
from ..register import register
#register
class Beta(object):
pass
As it stands, importing the package above will not result in any of the classes being registered. This is because the class definitions are never run, since the modules containing them are never imported. The remedy is to automatically generate an __init__.py for the plugins folder. Below is a script which does exactly this -- this script can be made part of your compilation process.
import pathlib
root = pathlib.Path('./mypkg/plugins')
exclude = {'__init__.py'}
def gen_modules(root):
for entry in root.iterdir():
if entry.suffix == '.py' and entry.name not in exclude:
yield entry.stem
with (root / '__init__.py').open('w') as fh:
for module in gen_modules(root):
fh.write('from . import %s\n' % module)
Placing this script one directory above your package root (assuming your package is called mypkg) and running it yields:
from . import alpha
from . import beta
Now for the test: we compile the package:
nuitka --module mypkg --recurse-to=mypkg
and try importing it, checking to see if all of the classes were properly registered:
>>> import mypkg
>>> mypkg.register.registry
{'Beta': <class 'mypkg.plugins.beta.Beta'>,
'Alpha': <class 'mypkg.plugins.alpha.Alpha'>}
Note that the same approach will work with using metaclasses to register the plugin classes, I simply preferred to use decorators here.

If the reflected classes are using your metaclass, you don't need to use from X import * to get them registered. Only import X should be enough. As soon as the module containing the classes is imported, the classes will be created and available in your metaclass registry.

I would do this with dynamic imports.
models/regression/base.py:
class Base(object):
def get_type(self):
return "BASE"
models/regression/subclass.py:
from models.regression.base import Base
class SubClass(Base):
def get_type(self):
return "SUB_CLASS"
__myclass__ = SubClass
loader.py:
from importlib import import_module
class_name = "subclass"
module = import_module("models.regression.%s" % class_name)
model = module.__myclass__()
print(model.get_type())
And empty __init__.py files in models/ and models/regression/
With:
nuitka --recurse-none --recurse-directory models --module loader.py
The resulting loader.so contains all the modules under the models/ subdirectory.

django abstract model inheritance import

I wonder how i can import an abstract model into another app
world_elements holds:
class Location(models.Model):
"""
Holds x,y coordinates of a virtual 2d map.
"""
x = models.IntegerField()
y = models.IntegerField()
class Meta:
abstract = True
def __unicode__(self):
return "%s, %s" % (self.x, self.y)
now in another app i try:
from world_elements.models import Location
class NpcTown(Location):
"""
A town with their coordinates trianinggrounds quest office and all other relevant attributes
"""
# general town information
name = models.CharField(max_length = 63)
flavor = models.TextField(max_length = 511)
guild = models.ForeignKey(NpcGuild)
# locations
trainingground = models.ForeignKey(TrainingGround, null=True)
def __unicode__(self):
return self.name
but now i get ImportError: cannot import name Location
How do i import an abstract model?

Simplifying the names of the classes a bit, the following works for me
in Django 1.7, which is the latest stable release at the time of this
writing.
Directory layout
project
\_ apps
\_ __init__.py
\_ A
\_ B
\_ config
\_ __init__.py
\_ settings.py
\_ urls.py
\_ wsgi.py
\_ data
\_ makefile
\_ manage.py
\_ README.md
In the above, app A contains the abstract model. B uses it, as
follows:
Abstract Class(es)
class AModel(Model):
...
class Meta:
abstract = True
Then
Concrete Class(es)
from apps.A.models import AModel
class BModel(AModel):
...
blah = "ayyo"
Note that apps, A, and B all must contain an __init__.py file.
Don't be afraid to break free of the Django directory layout conventions
imposed by manage.py start{app,project}. Doing so will free your mind
and you will love having things neatly organized.
Another thing that helps debugging module imports is simply printing
the module imported. Then you can tell what is actually being resolved.
For example:
from apps.A.models import AModel
print AModel # <class 'apps.A.models.AModel'>
And:
import apps
print apps # <module 'apps' from '/home/g33k/gits/checkouts/my/project/apps/__init__.pyc'>

In a normal structure like this:
my_project
- /my_project
- /settings.py
- /app1
- /models.py
* class Model1...
- /app2
- /models.py
* class Model2...
From app1/models.py this worked for me:
from django.db import models
from my_project.app1.models import Model1
class Model2(Model1):
...
Using Django 11.1

Try
from world_elements import Location

Python class method throws AttributeError

I'm having issues getting a class method to run in Flask.
In models/User.py:
from mongoengine import *
class User(Document):
first_name = StringField()
last_name = StringField()
...
def __init__(self, arg1, arg2, ...):
self.first_name = arg1
self.last_name = arg2
...
#classmethod
def create(self, arg1, arg2, ...):
#do some things like salting and hashing passwords...
user = self(arg1, arg2, ...)
user.save()
return user
In the main application python file:
from models import User
...
def func():
...
#Throws "AttributeError: type object 'User' has no attribute 'create'"
user = User.create(arg1, arg2, ...)
Shouldn't I be able to call create on the User class without instantiating a User object? I'm using Python 2.7.2, and I also tried the non-decorator syntax of using create = classmethod(create), but that didn't work. Thanks in advance!
EDIT: I found one issue: that the models folder did not contain an __init__.py file, so it wasn't a module, so from models import User was not actually importing the file I wanted it to. It did not give me an error from before because I used to have a models.py module in the same directory as the application python script, but after deleting it I never deleted the corresponding .pyc file. Now, I'm getting the error AttributeError: 'module' object has no attribute 'create' instead of what I had before, but I'm certain it is importing the correct file now.
EDIT2: Solved. I then changed the import to from models.User import User and It's hitting the method now.

The issue was twofold:
The User.py file was in the models/ folder, meaning that my import was actually looking for the User class in the models.py file, which no longer existed but still was being imported without error because the models.pyc file was still around
The import was incorrect for importing within a directory. it should have been from models.User import User, so long as the models/ folder is a module, so all I needed to do then was touch models/__init__.py.

>>> class foo(object):
... def __init__(self):
... pass
... #classmethod
... def classmethod(cls):
... return 0
...
>>> a = foo()
>>> a.classmethod()
0
>>>