Regex for house number

Question

Looking for a regex that specifies a German house number:

Valid house number:

• 12
• 12a
• 12A
• 12 A
• 12 a
• 12 b
• 12 z
• 121 b
• 56/58
• 56/58a
• 56-58
• 56 - 58
• 56-58a

Not valid house number:

• 25-ab
• 12ü
• 12_
• 12!"§$$%&/()
• a2
• a2
• 13àâäèéêë
• 0
• 123aaa123,
• 123 aaa 123
• 1 a 1
• 1a 1
• 1a1
• 00 a
• a a
• 00a
• 13àâäèéêëîïôœùûü

Only valid characters are: abcdefghijklmnopqrstuvwxyz

My regex doesn't match the way it should:

^[1-9]\d*(?:[ -]?(?:[a-zA-Z]+|[1-9]\d*))?$

Please see my example on regex101

Answer 1

A few notes about the pattern that you tried:

• The pattern gets 1 match too many as [a-zA-Z]+ matches 1 or more times.
• The pattern is not matching some values because this part [ -]? optionally matches a space or a hyphen and the / is not present in the character class
• This part 56 - 58 will not match as there is a space and a hyphen to be matched and the optional character class [ -]? will match only one of those
• This part 56-58a will not match, as there are no digits matched before the character class [a-zA-Z]

---

As an alternative, a bit shorter variant than I initially commented using an alternation and the case insensitive flag:

^[1-9]\d*(?: ?(?:[a-z]|[/-] ?\d+[a-z]?))?$

In parts

• ^ Start of string
• [1-9]\d* Match a digit 1-9 and optional digits 0-9
• (?: Non capture group
  • ? Match an optional space
  • (?: Non capture group (for the alternation)
    • [a-z] Match a char a-zA-Z (using case insensitive match enabled)
    • | Or
    • [/-] ? Match either / or / with optional space
    • \d+[a-z]? Match 1+ digits with optional char a-zA-Z
  • ) Close non capture group
• )? Close non capture group and make it optional
• $ Assert end of line (Or use \Z if there can not be a newline following)

Regex demo