Python isdigit() and None

[Gribouillis]

I don't know what the 'preset' instance is, but when objects have a get() method, this method often has a default argument. You could use this default argument. Example with dictionaries

>>> spam = {}
>>> spam.get('last')
>>> spam.get('last', '')
''
>>> spam.get('last', '').isdigit()
False
>>> spam.get('last').isdigit()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'isdigit'