在 python 正则表达式中的 Re.search 没有按预期工作

Question

QUESTION:

I am a beginner with python and using regex engine of python. I am able to match several sample regex patterns with my seed file but weirdly enough, I am unable to match lines in my sample file that contains the word "repeat." Below is the context of my issue. What could be the reason?

Sample Text:

import tset flash_read, flash_writ;

vector ( $tset, (XMOSI,XMISO,XSGLK,XSTRMSTRT,XSTRMSGLK,XSTRMGKEN,XXTALIN,XXTALGPUEN,XHV (XSTRM03,XSTRMO2,XSTRM01,XSTRIADO,XNSS3,XNSS2,XNSS1,XNSSOH, XTEGLOGK, XRXDATA, XRXENABLE, XTXDATA, XTXENABLE, XNRESET, ROOK, XTMS, XTDI, XTDO, XNTRST))

> flash_writ .d0000 .dFF 1 01 01 01 01 X 1; // write byte 0

> flash_writ .d0001 .dFF 1 0 1 0 1 01 01 X 1; // write byte 1

repeat 25> flash_writ .d0000 .d00 1 1 1 0001  0 1 X 1; // wait program time 
> flash_writ .d0002 .dFF 1 0 1 0 1 0 1 0 1 X 1; // write byte 0

> flash_writ .d0003 .dFF 1 0 1 0 1 0 1 0 1 X 1; // write byte 1

repeat 25> flash_writ .d0000 .d00 1 1 1 0001  0 1 X 1; // wait program time 
> flash_writ .d0004 .dFF 1 01 01 01 01 X1, 11 write byte 0

> flash_writ .d0005 .dFF 1 01 01 01 01 X1; // write byte 1

repeat 25> flash_writ .d0000 .d00 1 1 1 0001  0 1 X 1; // wait program time

Python Syntax Used for regex search:

regex_rep = r” repeat "

for num, eachline in enumerate(files_atp):

if re.search(regex_rep, eachline, flags=re.IGNORECASE) is not None:

      print eachline

THIS IS NOT WORKING (does not produce any matches)

Answer 1

Your pattern is:

regex_rep = r" repeat "

This will match the word repeat with a space on each end.

But your lines look like this:

repeat 25> flash_writ .d0000 .d00 1 1 1 0001  0 1 X 1; // wait program time

There's no space before repeat , so it doesn't match your pattern.

It's hard to suggest how to fix this, because I'm not sure why you put those spaces in the pattern in the first place.

---

If they're there for no reason, just get rid of them:

regex_rep = r"repeat"

However, in that case, you're not using any features of re at all, so your test would be better written as:

if "repeat" in eachline:

---

If they're there to make the pattern more readable, and you want re to ignore the spaces, you can use the VERBOSE flag to tell it to ignore spaces in your pattern:

if re.search(regex_rep, eachline, flags=re.IGNORECASE|re.VERBOSE) is not None:

You can see this working at regex101 .

---

If you want to make sure you're matching repeat as a whole word, rather than as part of a larger word like repeatable , you can use the \\b special character, which:

Matches the empty string, but only at the beginning or end of a word…

regex_rep = r"\brepeat\b"

You can see this in action at regex101 .