Finding What Methods a Python Object Has

Finding what methods a Python object has

For many objects, you can use this code, replacing 'object' with the object you're interested in:

object_methods = [method_name for method_name in dir(object)
                  if callable(getattr(object, method_name))]

I discovered it at diveintopython.net (now archived), that should provide some further details!

If you get an AttributeError, you can use this instead:

getattr() is intolerant of pandas style Python 3.6 abstract virtual sub-classes. This code does the same as above and ignores exceptions.

import pandas as pd
df = pd.DataFrame([[10, 20, 30], [100, 200, 300]],
                  columns=['foo', 'bar', 'baz'])
def get_methods(object, spacing=20):
  methodList = []
  for method_name in dir(object):
    try:
        if callable(getattr(object, method_name)):
            methodList.append(str(method_name))
    except Exception:
        methodList.append(str(method_name))
  processFunc = (lambda s: ' '.join(s.split())) or (lambda s: s)
  for method in methodList:
    try:
        print(str(method.ljust(spacing)) + ' ' +
              processFunc(str(getattr(object, method).__doc__)[0:90]))
    except Exception:
        print(method.ljust(spacing) + ' ' + ' getattr() failed')

get_methods(df['foo'])

How do I get list of methods in a Python class?

An example (listing the methods of the optparse.OptionParser class):

>>> from optparse import OptionParser
>>> import inspect
#python2
>>> inspect.getmembers(OptionParser, predicate=inspect.ismethod)
[([('__init__', <unbound method OptionParser.__init__>),
...
 ('add_option', <unbound method OptionParser.add_option>),
 ('add_option_group', <unbound method OptionParser.add_option_group>),
 ('add_options', <unbound method OptionParser.add_options>),
 ('check_values', <unbound method OptionParser.check_values>),
 ('destroy', <unbound method OptionParser.destroy>),
 ('disable_interspersed_args',
  <unbound method OptionParser.disable_interspersed_args>),
 ('enable_interspersed_args',
  <unbound method OptionParser.enable_interspersed_args>),
 ('error', <unbound method OptionParser.error>),
 ('exit', <unbound method OptionParser.exit>),
 ('expand_prog_name', <unbound method OptionParser.expand_prog_name>),
 ...
 ]
# python3
>>> inspect.getmembers(OptionParser, predicate=inspect.isfunction)
...

Notice that getmembers returns a list of 2-tuples. The first item is the name of the member, the second item is the value.

You can also pass an instance to getmembers:

>>> parser = OptionParser()
>>> inspect.getmembers(parser, predicate=inspect.ismethod)
...

Can i get all methods of a python object?

you need see inspect. For example

inspect.getmembers(object, inspect.ismethod)

it returns only method.

Get all object attributes in Python?

Use the built-in function dir().

How do I check the methods that an object has, in Python?

You can use dir to get a list the methods of any object. This is very useful in the interactive prompt:

>>> dir(l1)
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__delslice__', '__doc__', '__eq__',
'__ge__', '__getattribute__', '__getitem__', '__getslice__', '__gt__', '__hash__', '__iadd__', '__imul__',
'__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__',
'__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__setslice__',
'__str__', 'append', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

The interesting methods are usually those not starting with underscores. You can write your own version of dir that ignores names starting with underscores if you wish:

>>> mydir = lambda a:[x for x in dir(a) if not x.startswith('_')]
>>> mydir([])
['append', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

Determine the type of an object?

There are two built-in functions that help you identify the type of an object. You can use type() if you need the exact type of an object, and isinstance() to check an object’s type against something. Usually, you want to use isinstance() most of the times since it is very robust and also supports type inheritance.

---

To get the actual type of an object, you use the built-in type() function. Passing an object as the only parameter will return the type object of that object:

>>> type([]) is list
True
>>> type({}) is dict
True
>>> type('') is str
True
>>> type(0) is int
True

This of course also works for custom types:

>>> class Test1 (object):
        pass
>>> class Test2 (Test1):
        pass
>>> a = Test1()
>>> b = Test2()
>>> type(a) is Test1
True
>>> type(b) is Test2
True

Note that type() will only return the immediate type of the object, but won’t be able to tell you about type inheritance.

>>> type(b) is Test1
False

To cover that, you should use the isinstance function. This of course also works for built-in types:

>>> isinstance(b, Test1)
True
>>> isinstance(b, Test2)
True
>>> isinstance(a, Test1)
True
>>> isinstance(a, Test2)
False
>>> isinstance([], list)
True
>>> isinstance({}, dict)
True

isinstance() is usually the preferred way to ensure the type of an object because it will also accept derived types. So unless you actually need the type object (for whatever reason), using isinstance() is preferred over type().

The second parameter of isinstance() also accepts a tuple of types, so it’s possible to check for multiple types at once. isinstance will then return true, if the object is of any of those types:

>>> isinstance([], (tuple, list, set))
True

Is there a function in Python to list the attributes and methods of a particular object?

You want to look at the dir() function:

>>> li = []
>>> dir(li)      
['append', 'count', 'extend', 'index', 'insert',
'pop', 'remove', 'reverse', 'sort']

li is a list, so dir(li) returns a list of all the methods of a list. Note that the returned list contains the names of the methods as strings, not the methods themselves.

---

Edit in response to comment:

No this will show all inherited methods as well. Consider this example:

test.py:

class Foo:
    def foo(): pass

class Bar(Foo):
    def bar(): pass

Python interpreter:

>>> from test import Foo, Bar
>>> dir(Foo)
['__doc__', '__module__', 'foo']
>>> dir(Bar)
['__doc__', '__module__', 'bar', 'foo']

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You should note that Python's documentation states:

Note: Because dir() is supplied
primarily as a convenience for use at
an interactive prompt, it tries to
supply an interesting set of names
more than it tries to supply a
rigorously or consistently defined set
of names, and its detailed behavior
may change across releases. For
example, metaclass attributes are not
in the result list when the argument
is a class.

Therefore it's not safe to use in your code. Use vars() instead. Vars() doesn't include information about the superclasses, you'd have to collect them yourself.

---

If you're using dir() to find information in an interactive interpreter, consider the use of help().

Getting all class methods in classes in current file in Python?

On Python 3, calling inspect.ismethod on an attribute of a class that happens to be a function will always be False, because it will just be a plain function. function.__get__ only returns a method object when accessed as an attribute of an instance.

If you want to get all "methods" of the class just use inspect.isfunction.

>>> class A:
...     def __init__(self): pass
... 
>>> A.__init__
<function A.__init__ at 0x7fd524dd2f80>
>>> inspect.ismethod(A.__init__)
False
>>> inspect.isfunction(A.__init__)
True
>>> inspect.ismethod(A().__init__)
True

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