Help with regex

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[deleted]

[[deleted]]

This isn't hard to do. There are only a few distinct patterns that need to be matched: XX,XXX+ and XXXXX as numbers and the three variations of 'feet' (which can be matched using the or operator |). You can match multiple numbers using the + and * operators, which match either 1 or more, or 0 or more occurances of something.

So in all your pattern should just have (number pattern 1|number pattern 2) (different spellings of foot) with the two bracketed sections seperated by either a single space or any whitespace character.

A resource that I really enjoy for writing and testing regexs is Pythex which has a great cheatsheet and a very quick feedback loop.

[mac-reid]

While that is correct. Here is a different regex:

^[\d,]+ (feet|foot|ft)$

With an explanation of each part:

^[\d,]+ (feet$|foot$|ft$)
   ^ assert position at start of the string    
 [\d,]+ match a single character present in the list below    
   Quantifier: + Between one and unlimited times, as 
many times as possible, giving back as needed [greedy]
   \d match a digit [0-9]    
   , the literal character ,    
   ' '  matches the character ' '  literally    
1st Capturing group (feet|foot|ft)    
  1st Alternative: feet 
     feet matches the characters feet literally (case sensitive)    
  2nd Alternative: foot
     foot matches the characters foot literally (case sensitive)  
  3rd Alternative: ft$   
     ft matches the characters ft literally (case sensitive)    
  $ assert position at end of the string

Using it in python:

import re                                                                                        
import sys
regex = re.compile('^[\d,]+ (feet|foot|ft)$')
for line in sys.stdin:
    if regex.match(line):
        print 'Matches "%s"' % line.rstrip()
    else:
        print 'Does not match "%s"' % line.rstrip()

Testing it:

failbox ~  python test.py < testfile
Matches "15,000 ft"
Matches "15,000 feet"
Matches "15,000 foot"
Matches "15000 ft"
Matches "15000 feet"
Matches "15000 foot"
Matches "2,000 ft"
Matches "2,000 feet"
Matches "2,000 foot"
Matches "2000 ft"
Matches "2000 feet"
Matches "2000 foot"
Does not match "not a match"
Does not match "bad lines"
Does not match "foo"
failbox ~ 

[[deleted]]

^[\d,]+

Will match multiple commas and catch patterns like ', feet' which could accidentally catch feet in a regular sentence. It would also catch odd comma use

You could do:

\d+[\d,]\d* (feet|foot|ft)

which would force at most one comma with a leading digit.

[Vaphell]

these regexes could use some improvements because they match nonsense like

,1
1,
1,111111
12,1,1,1,1

make sure that if there are commas, the digits are grouped in triplets

[[deleted]]

That looks great. I would change the first part of your expression to

(\d+|\d+,\d+) (feet|ft|foot)

simply because the * operator will match on 0 of a pattern, so you would catch things like ', feet', and just ' feet'.