How To Check Whether A Method Exists In Python?

In the function __getattr__(), if a referred variable is not found then it gives an error. How can I check to see if a variable or method exists as part of an object? import string

Solution 1:

Check if class has such method?

hasattr(Dynamo, key) and callable(getattr(Dynamo, key))

or

hasattr(Dynamo, 'mymethod') andcallable(getattr(Dynamo, 'mymethod'))

You can use self.__class__ instead of Dynamo

Solution 2:

It's easier to ask forgiveness than to ask permission.

Don't check to see if a method exists. Don't waste a single line of code on "checking"

try:
    dyn.mymethod() # How to check whether this exists or not# Method exists and was used.  except AttributeError:
    # Method does not exist; What now?

Solution 3:

How about dir() function before getattr()?

>>> "mymethod"indir(dyn)
True

Solution 4:

I use below utility function. It works on lambda, class methods as well as instance methods.

Utility Method

defhas_method(o, name):
    returncallable(getattr(o, name, None))

Example Usage

Let's define test class

classMyTest:
  b = 'hello'
  f = lambda x: x

  @classmethoddeffs():
    passdeffi(self):
    pass

Now you can try,

>>>a = MyTest()                                                    >>>has_method(a, 'b')                                         
False                                                          
>>>has_method(a, 'f')                                         
True                                                           
>>>has_method(a, 'fs')                                        
True                                                           
>>>has_method(a, 'fi')                                        
True                                                           
>>>has_method(a, 'not_exist')                                       
False                                                          

Solution 5:

You can try using 'inspect' module:

import inspect
defis_method(obj, name):
    returnhasattr(obj, name) and inspect.ismethod(getattr(obj, name))

is_method(dyn, 'mymethod')