This would allow a string of one or more spaces to match, which raises an exception if `int()` is applied to it:

```python
>>> import re
>>> count_re = re.compile('^ *[0-9]* ')
>>> s = " abc"
>>> count_re.findall(s)
[' ']
>>> int(count_re.findall(s)[0])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: ''
```
Wouldn't you want to make sure that at least some number does get matched if there is a match?