please could some one understand what i am saying i need a program that can count number of digit in a number given by the user .for example if we see123 it has 3 digits...?

Convert to string and use len(),is the most commen way.

>>> n = 123
>>> len(str(n))
3
>>>

If your user input is returning a string like raw_input() in python 2.x and input() in python 3.x you can use len().
Then convert to integer if needed.
You can make function that takes integer as argument,and returning the lenght out.
A couple of example.

>>> u = raw_input('Enter a number')
Enter a number
>>> u = raw_input('Enter a number: ')
Enter a number: 123
>>> len(u)
3
>>> int(u) + 123
246
#A function
>>> def lenght(n):
return len(str(n))
>>> lenght(12345)
5
>>>

Without converting to string.

import math
digits = int(math.log10(12345))+1
print digits #5