How do I override __getattr__ without breaking the default behavior?

by

Overriding __getattr__ should be fine — __getattr__ is only called as a last resort i.e. if there are no attributes in the instance that match the name. For instance, if you access foo.bar, then __getattr__ will only be called if foo has no attribute called bar. If the attribute is one you don’t want to handle, raise AttributeError:

class Foo(object):
    def __getattr__(self, name):
        if some_predicate(name):
            # ...
        else:
            # Default behaviour
            raise AttributeError

However, unlike __getattr__, __getattribute__ will be called first (only works for new style classes i.e. those that inherit from object). In this case, you can preserve default behaviour like so:

class Foo(object):
    def __getattribute__(self, name):
        if some_predicate(name):
            # ...
        else:
            # Default behaviour
            return object.__getattribute__(self, name)

See the Python docs for more.

More Related Contents:

  1. How do I use getattr and setattr properly in Python? [closed]
  2. What is getattr() exactly and how do I use it?
  3. Difference between __getattr__ and __getattribute__
  4. __getattr__ on a module
  5. How do I implement __getattribute__ without an infinite recursion error?
  6. How do I call setattr() on the current module?
  7. How to use __setattr__ correctly, avoiding infinite recursion
  8. Recursively access dict via attributes as well as index access?
  9. Understanding the difference between __getattr__ and __getattribute__
  10. __getattr__ for static/class variables
  11. How do I parse a string to a float or int?
  12. Python Variable Declaration
  13. Weird Try-Except-Else-Finally behavior with Return statements
  14. Python find elements in one list that are not in the other [duplicate]
  15. Pandas: Get Dummies
  16. Find the item with maximum occurrences in a list [duplicate]
  17. Comparing previous row values in Pandas DataFrame
  18. Counting unique values in a column in pandas dataframe like in Qlik?
  19. What exactly is Python multiprocessing Module’s .join() Method Doing?
  20. Python file.tell() giving strange numbers?
  21. problems with pygame controller support
  22. Python pandas / matplotlib annotating labels above bar chart columns [duplicate]
  23. How to upsert pandas DataFrame to PostgreSQL table?
  24. How can I check if two strings are anagrams of each other?
  25. Inserting the same value multiple times when formatting a string
  26. How to create raw string from string variable in python?
  27. Resize fields in Django Admin
  28. How do I get the user agent with Flask?
  29. Creating a list in Python with multiple copies of a given object in a single line
  30. Pytorch ValueError: optimizer got an empty parameter list

Leave a Comment