Python re Regular Expression (Regex) Positive Look Behind

Ignition
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1

Hello,

I’m struggling with regex (re) expression in ignition. The expression works in a regex tester, but does not work in ignition. The weird thing is that only the negative lookbehind is not working. I have other regular expression matches and they are working as normal.

Here is a snapshot of my expression functioning in a regex test environment. It successfully matches the two digits after ‘TDY’.
image

However, when I run this same expression and string in ignition I get no matches:
image

2

re.match() looks at the begnning of the string for the match. Try using re.search() or re.findall() instead.

import re

pattern = r'(?<=TDY)[0-9][1-9]'
stringIn = '/XYZ01/TDY01/L01'

# using re.findall
print re.findall(pattern, stringIn)

# using re.search
search = re.search(pattern, stringIn)
if search:
	print 'Found:', search.group()
else:
	print 'Not found'

output:

['01']
Found: 01
2 Likes
3

The difference between re.search and re.match has bitten me many times.

2 Likes
4

Ah thank you @JordanCClark. That solved my problem. I guess I just assumed that a match would work since I was getting the result I was looking with the online tester while having the match function selected.

Thank you for the quick help!

1 Like