Meaning of result returned by Cohesion

[Marlysson]

I ran the lib cohesion over my code and return me the result.. what the lib analyze ?

 Function: __eq__ 1/3 33.33%
    Function: __init__ 1/3 33.33%
    Function: __repr__ 2/3 66.67%
    Function: change_bit 2/3 66.67%
    Function: is_valid 1/3 33.33%
    Total: 46.67%
  Class: Hamming
    Function: __init__ 1/13 7.69%
    Function: __repr__ 2/13 15.38%
    Function: bits_verified_by 3/13 23.08%
    Function: calculate_parity 2/13 15.38%
    Function: check 4/13 30.77%
    Function: divisors 1/13 7.69%
    Function: encode 8/13 61.54%
    Function: fix 3/13 23.08%
    Function: is_power 2/13 15.38%
    Function: wrong_position 4/13 30.77%
    Total: 23.08%

[mschwager]

You can read up on the concept of code cohesion here.

Basically, it measures how well a class is structured as a logical unit. This tool tells you what percentage of instance variables a class method uses. So if class Cls has instance variables self.instance1 and self.instance2, and member function func only uses self.instance1 then it will get 1/2 or 50% cohesion:

class Cls(object):
    def __init__(self):
        self.instance1 = 5
        self.instance2 = 6

    def func(self):
        return self.instance1 + 10

The rationale being that classes with member functions that use a large percentage of the instance variables available have strongly related functionality. Classes that have many instances variables that only get used in a few places would probably be better suited as multiple, different classes.

High cohesion is when you have a class that does a well defined job. Low cohesion is when a class does a lot of jobs that don't have much in common.

• http://stackoverflow.com/a/10830225