The following code in **Python **counts digits in a given number.

```
# this function returns number of digits
# in a given integer
def digits(n):
count = 0
if n == 0:
return 1
while (n >= 1):
count += 1
n = n/10
return count
# test cases
print(digits(25)) # should print 2
print(digits(144)) # should print 3
print(digits(1000)) # should print 4
print(digits(0)) # should print 1
```