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Regex-How to split string by delimiter and if there is no delimiter return whole

I would like to extract some information from a string like below:

ksdfXX2344_vvs_gfedfg
ksdfXX2344

For example, to extract word ksdfXX2344 from the string above.
Currently I have:

(.*?)(_.*)

which can extract the words in situation 1, but cannot extract the string with no delimiter _. How can I extract the words if there are no delimiter inside? Any suggestions?

Many thanks!

Solution

  • Don't split, replace:

    Search: '_.*'
Replace: ''

    eg in java:

    String prefix = str.replaceAll("_.*", "");

    or python:

    prefix = re.sub(r'_.*', '', str)

    To match only the prefix:

    ^[^_]*

    this matches everything at the start that isn't an underscore, so the match will stop before the first underscore or end-of-input if there isn't an underscore.