如何通过正则表达式检查字符串

Question

There is a such string - 1,2,3;45,25,65;4,2,78 . And I want to check it by regex such that:

• Number of digits of substring before the semicolon is constant for every substring before the semicolon. For example in the string above this number is 3.
• String does not end by semicolon ( ; ).

Examples of strings:

• 1,2,3;3,4,7 matched
• 1,2,3 matched
• 1,2;3,4; does not match (because of ; at the end)

Answer 1

If you want to do this with regexp, you are forced to specify the constant. This is the generic regex:

^\d+(,\d){n-1}(;\d+(,\d){n-1})*$

Where n-1 is your constant subtracting 1 (in the example above, n-1 = 2 ). See demo .

---

The iterative method instead always work:

def my_match(s) :
  k = None
  for arr in s.split(";") :
    length = len(arr.split(","))
    if k :
      if k != length : return False
    else :
      k = length
  return True

input = "1,2,3;45,25,65;4,2,78" # we assume that the input synthax is correct
print my_match(input)

If you don't assume that the input synthax is correct, use first Tim Biegeleisen's regex (something like ^\\d+(,\\d)*(;\\d+(,\\d)*)*$ ) for validating and then the method above.