Topic: Need Help Parsing a String

[Bill Tillman]

I have a bunch of data I'm working with and one of the fields is in this format:

   ABCxxXxxABCjklMZ

Or basically, the first three characters will always be string, then next one, two or possibly three characters will be integers from 0 to 9, then an upper case X followed by one, two or three integers 0 to 9. At this point of the string is where I want to discard everything to the left side of the last integer and grab anything and everything that's to the right of it. I'm pretty sure I can do this with some code, but this looks like it might be a good time for a regular expression. Not being too familiar with them I was hoping to get some advice here.

There may be times when a user puts an upper case X in one of the first three characters so if I do key in on that upper case X between the sets of integers, I'd have to take that into account. But most of the time, that upper case X will occur only between the sets of integers which may contain 1 to 3 digits each. And one set will not always be the same length as the other.

[ChrisCarlson]

Code: [Select]

/[A-Z]\D+$/ig

Potentially?

Should match

ABC11X11ABCjklMZ

[Jeff H]

If I read it correctly and not wanting to use regex
Then can chain some string functions.
Here is a simple console program that has a one-liner and a step by by function

one-liner

Code - C#: [Select]

1. String.Concat(input.Substring(input.IndexOf('X', 3) + 1).SkipWhile(Char.IsNumber));
2.  

 
one-liner function with a step by step function

Code - C#: [Select]

1.  
2. class Program
3.     {
4.         static void Main(string[] args)
5.         {
6.             string[] inputs = new[] { "XxC12X6ABCjklMZ", "ABC12X21ABCjklMZ", "XXX1X21ABCjklMZ" };
7.  
8.  
9.             foreach (var input in inputs)
10.             {
11.                 Console.WriteLine(ParseField(input));
12.             }
13.  
14.  
15.             foreach (var input in inputs)
16.             {
17.                 ParseFieldbyStep(input);
18.             }
19.             Console.ReadKey();
20.  
21.  
22.         }
23.  
24.  
25.         static string ParseField(string input)
26.         {
27.             return String.Concat(input.Substring(input.IndexOf('X', 3) + 1).SkipWhile(Char.IsNumber));
28.         }
29.  
30.  
31.        
32.         static void ParseFieldbyStep(string input)
33.         {
34.             Console.WriteLine();
35.             Console.WriteLine(input);
36.             var removeFirst3chars = input.Substring(3);
37.             Console.WriteLine(removeFirst3chars + "  - First 3 char removed");
38.  
39.  
40.             var indexOfFirstX = removeFirst3chars.IndexOf('X');
41.             Console.WriteLine(indexOfFirstX + "  = Index of First X in \"" + removeFirst3chars +"\"");
42.  
43.  
44.             var indexAfterFirstX = indexOfFirstX + 1;
45.             var stringAfterFirstX = removeFirst3chars.Substring(indexAfterFirstX);
46.             Console.WriteLine(stringAfterFirstX + "  - string after X ");
47.            
48.             int numberIndex = 0;
49.             while (Char.IsNumber(stringAfterFirstX[numberIndex]))
50.             {
51.                 Console.WriteLine(stringAfterFirstX[numberIndex] + "  - is a number");
52.                 numberIndex++;
53.             }
54.  
55.  
56.             Console.WriteLine(stringAfterFirstX[numberIndex] + "  - first non-number");
57.  
58.  
59.             var result = stringAfterFirstX.Substring(numberIndex);
60.             Console.WriteLine("Result = " + result);
61.         }
62.  
63.  
64.     }
65.  

[CADbloke]

I have a bunch of data I'm working with and one of the fields is in this format:

   ABCxxXxxABCjklMZ

... I want to discard everything to the left side of the last integer and grab anything and everything that's to the right of it. I'm pretty sure I can do this with some code, but this looks like it might be a good time for a regular expression.

Code - C#: [Select]

1. string resultString = null;
2. try {
3.         resultString = Regex.Replace(subjectString, @"(?:.*)(\d)(?!.*\d)(.*)", "$1$2", RegexOptions.IgnoreCase | RegexOptions.Multiline);
4. } catch (ArgumentException ex) {
5.         // Syntax error in the regular expression
6. }

Do you want to grab the last integer? if yes, keep the $1 in the replacement, otherwise your replacement is $2.

See the screengrab for an explanation, that's http://www.regexbuddy.com/ and it's worth every cent. See also http://www.regexbuddy.com/regexmagic.html

edit: yay regex, of course I got it wrong on the 1st attempt. Also, added a test in AutoCAD (no, you haven't seen that plugin before)

moar edit: this may be a clearer explanation (RegexBuddy generated this)...

Code - C#: [Select]

1. @"
2. (?:        # Match the regular expression below
3.   .          # Match any single character that is NOT a line break character (line feed)
4.      *          # Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
5. )
6. (          # Match the regex below and capture its match into backreference number 1
7.   \d         # Match a single character that is a “digit” (any decimal number in any Unicode script)
8. )
9. (?!        # Assert that it is impossible to match the regex below starting at this position (negative lookahead)
10.   .          # Match any single character that is NOT a line break character (line feed)
11.      *          # Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
12.   \d         # Match a single character that is a “digit” (any decimal number in any Unicode script)
13. )
14. (          # Match the regex below and capture its match into backreference number 2
15.   .          # Match any single character that is NOT a line break character (line feed)
16.      *          # Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
17. )
18. "
19.  

[Bill Tillman]

Thanks. You guys are awesome. I'm reading lots more about regex stuff this week and it's really cool.

[ChrisCarlson]

I just can't understand regex but this site http://www.regexr.com/ has helped me quite a bit figuring individual ones out

[CADbloke]

this site http://www.regexr.com/ has helped me quite a bit figuring individual ones out

FYI there are differences between the different Regex Engines, that one uses the  Javascript parser, the .NET engine is slightly different in places. http://www.regular-expressions.info/ is a great site by the guy who wrote RegexBuddy. http://stackoverflow.com/questions/22937618/reference-what-does-this-regex-mean/22944075#22944075 has more information than you could probably ever read.

[Tuoni]

Some people, when confronted with a problem, think “I know, I'll use regular expressions.”  Now they have two problems.

 

[CADbloke]

Some people, when confronted with a problem, think “I know, I'll use regular expressions.”  Now they have two problems.

 

heheh, for more on that ... http://blog.codinghorror.com/regular-expressions-now-you-have-two-problems/

BTW, it's a lot more  than 2 - http://blog.codinghorror.com/regex-performance/ &  http://www.regular-expressions.info/catastrophic.html

TLDR; it is entirely feasible that a badly done Regex can take days to compute. Whups.

.NET 4.5 has a timeout property because of this. Don't let that scare you, I have found them to be fast and I still have all my fingers.

[BlackBox]

Disclaimer: Newest post I could find that seemed relevant.


Just wanted to share this site, which yielded a usable RegEx 'match' Method in seconds - highly recommend :

http://txt2re.com/index-csharp.php3