unbound method f() must be called with fibo_ instance as first argument (got classobj instance instead)

Question

In Python, I\'m trying to run a method in a class and I get an error:

Traceback (most recent call last):
  File \"C:\\Users\\domenico\\Desktop\\py\\main.py\"         


        

Answer 1

How to reproduce this error with as few lines as possible:

>>> class C:
...   def f(self):
...     print "hi"
...
>>> C.f()
Traceback (most recent call last):
  File "", line 1, in 
TypeError: unbound method f() must be called with C instance as 
first argument (got nothing instead)

It fails because of TypeError because you didn't instantiate the class first, you have two choices: 1: either make the method static so you can run it in a static way, or 2: instantiate your class so you have an instance to grab onto, to run the method.

It looks like you want to run the method in a static way, do this:

>>> class C:
...   @staticmethod
...   def f():
...     print "hi"
...
>>> C.f()
hi

Or, what you probably meant is to use the instantiated instance like this:

>>> class C:
...   def f(self):
...     print "hi"
...
>>> c1 = C()
>>> c1.f()
hi
>>> C().f()
hi

If this confuses you, ask these questions:

1. What is the difference between the behavior of a static method vs the behavior of a normal method?
2. What does it mean to instantiate a class?
3. Differences between how static methods are run vs normal methods.
4. Differences between class and object.