Get fully qualified class name of an object in Python

Question

For logging purposes I want to retrieve the fully qualified class name of a Python object. (With fully qualified I mean the class name including the package and module name.)

I know about x.__class__.__name__, but is there a simple method to get the package and module?

Answer 1

With the following program

#!/usr/bin/env python

import foo

def fullname(o):
    klass = o.__class__
    module = klass.__module__
    if module == 'builtins':
        return klass.__qualname__ # avoid outputs like 'builtins.str'
    return module + '.' + klass.__qualname__

bar = foo.Bar()
print(fullname(bar))

and Bar defined as

class Bar(object):
  def __init__(self, v=42):
    self.val = v

the output is

$ ./prog.py
foo.Bar

If you're still stuck on Python 2, you'll have to use __name__ instead of __qualname__, which is less informative for nested classes - a class Bar nested in a class Foo will show up as Bar instead of Foo.Bar:

def fullname(o):
    klass = o.__class__
    module = klass.__module__
    if module == '__builtin__':
        return klass.__name__ # avoid outputs like '__builtin__.str'
    return module + '.' + klass.__name__

Answer 2

The provided answers don't deal with nested classes. Though it's not available until Python 3.3 (PEP 3155), you really want to use the __qualname__ of the class instead of the __name__. Otherwise, a class like

class Foo:
    class Bar: # this one
        pass

will show up as just Bar instead of Foo.Bar.

(You'll still need to attach the __module__ to the qualname separately - __qualname__ is not intended to include module names.)

Answer 3

Here's one based on Greg Bacon's excellent answer, but with a couple of extra checks:

__module__ can be None (according to the docs), and also for a type like str it can be __builtin__ (which you might not want appearing in logs or whatever). The following checks for both those possibilities:

def fullname(o):
    module = o.__class__.__module__
    if module is None or module == str.__class__.__module__:
        return o.__class__.__name__
    return module + '.' + o.__class__.__name__

(There might be a better way to check for __builtin__. The above just relies on the fact that str is always available, and its module is always __builtin__)

Answer 4

Consider using the inspect module which has functions like getmodule which might be what are looking for:

>>>import inspect
>>>import xml.etree.ElementTree
>>>et = xml.etree.ElementTree.ElementTree()
>>>inspect.getmodule(et)
<module 'xml.etree.ElementTree' from 
        'D:\tools\python2.5.2\lib\xml\etree\ElementTree.pyc'>

Answer 5

For python3.7 I use:

".".join([obj.__module__, obj.__name__])

Getting:

package.subpackage.ClassName

Answer 6

__module__ would do the trick.

Try:

>>> import re
>>> print re.compile.__module__
re

This site suggests that __package__ might work for Python 3.0; However, the examples given there won't work under my Python 2.5.2 console.

Answer 7

Some people (e.g. https://stackoverflow.com/a/16763814/5766934) arguing that __qualname__ is better than __name__. Here is an example that shows the difference:

$ cat dummy.py 
class One:
    class Two:
        pass

$ python3.6
>>> import dummy
>>> print(dummy.One)
<class 'dummy.One'>
>>> print(dummy.One.Two)
<class 'dummy.One.Two'>
>>> def full_name_with_name(klass):
...     return f'{klass.__module__}.{klass.__name__}'
>>> def full_name_with_qualname(klass):
...     return f'{klass.__module__}.{klass.__qualname__}'
>>> print(full_name_with_name(dummy.One))  # Correct
dummy.One
>>> print(full_name_with_name(dummy.One.Two))  # Wrong
dummy.Two
>>> print(full_name_with_qualname(dummy.One))  # Correct
dummy.One
>>> print(full_name_with_qualname(dummy.One.Two))  # Correct
dummy.One.Two

Note, it also works correctly for builtins:

>>> print(full_name_with_qualname(print))
builtins.print
>>> import builtins
>>> builtins.print
<built-in function print>

Answer 8

This is a hack but I'm supporting 2.6 and just need something simple:

>>> from logging.handlers import MemoryHandler as MH
>>> str(MH).split("'")[1]

'logging.handlers.MemoryHandler'

Answer 9

Since the interest of this topic is to get fully qualified names, here is a pitfall that occurs when using relative imports along with the main module existing in the same package. E.g., with the below module setup:

$ cat /tmp/fqname/foo/__init__.py
$ cat /tmp/fqname/foo/bar.py
from baz import Baz
print Baz.__module__
$ cat /tmp/fqname/foo/baz.py
class Baz: pass
$ cat /tmp/fqname/main.py
import foo.bar
from foo.baz import Baz
print Baz.__module__
$ cat /tmp/fqname/foo/hum.py
import bar
import foo.bar

Here is the output showing the result of importing the same module differently:

$ export PYTHONPATH=/tmp/fqname
$ python /tmp/fqname/main.py
foo.baz
foo.baz
$ python /tmp/fqname/foo/bar.py
baz
$ python /tmp/fqname/foo/hum.py
baz
foo.baz

When hum imports bar using relative path, bar sees Baz.__module__ as just "baz", but in the second import that uses full name, bar sees the same as "foo.baz".

If you are persisting the fully-qualified names somewhere, it is better to avoid relative imports for those classes.

Answer 10

None of the answers here worked for me. In my case, I was using Python 2.7 and knew that I would only be working with newstyle object classes.

def get_qualified_python_name_from_class(model):
    c = model.__class__.__mro__[0]
    name = c.__module__ + "." + c.__name__
    return name

Answer 11

This is an adaption of the answers by Greg Bacon and MB to use the qualified class name. Note that the question did ask for the qualified class name. It was tested with Python 3.8.

def fullname(obj: object) -> str:
    """Return the full name of the given object using its module and qualified class names."""
    # Ref: https://stackoverflow.com/a/66508248/
    module_name, class_name = obj.__class__.__module__, obj.__class__.__qualname__
    if module_name in (None, str.__class__.__module__):
        return class_name
    return module_name + "." + class_name