Python classes and modules

Question

I am teaching myself Python and hit a roadblock with classes and modules. The code below is something that you would probably never write, but I would like to just understand my error.

import random
class GetRandom:
 def __init__(self):
 self.data = ""
 def ranNumber():
 return random.random()
b = GetRandom()
bnum = b.ranNumber
print bnum

The output I am getting is:

<bound method GetRandom.ranNumber of <__main__.GetRandom instance at 0x7fe87818df38>>

I had expected a random number between 0 and 1. What am I doing wrong?

Thanks

Answer 1

There are two problems here:

1. You forgot to actually invoke GetRandom.ranNumber. Add () after it to do this:

   bnum = b.ranNumber()
   

2. You need to make GetRandom.ranNumber accept the self argument that is passed implicitly when you invoke the method:

   def ranNumber(self):
    return random.random()
   

Once you address these issues, the code works as expected:

>>> import random
>>> class GetRandom:
... def __init__(self):
... self.data = ""
... def ranNumber(self):
... return random.random()
...
>>> b = GetRandom()
>>> bnum = b.ranNumber()
>>> print bnum
0.819458844177
>>>