I have a Python regex for German house numbers which works okay. However, some pattern doesn't match as you can see in this demo.
These should be valid:
This should not be valid (because the number of digits is too long):
This is my regex:
^[1-9]\d*(?: ?(?:[a-zA-Z]|[/-] ?\d+[a-z]?))?$
You can use
^[1-9]\d{0,3} ?[a-zA-Z]?(?: ?[/-] ?[1-9]\d{0,3} ?[a-zA-Z]?)?$
See the regex demo.
Details
^ - start of string[1-9]\d{0,3} ?[a-zA-Z]? - a non-zero digit, then zero to three digits, then an optional space and then an optional letter(?: ?[/-] ?[1-9]\d{0,3} ?[a-zA-Z]?)? - an optional sequence of an optional space, / or -, an optional space and, like the part explained above, a non-zero digit, then zero to three digits, then an optional space and then an optional letter$ - end of string.