Perl正则表达式\ U.

Question

I am trying to convert some perl code to python. I came across this line

if($Var=~ /^\U/)
{ dosomething(); }

I have looked over the web for expression, but i am not able to comprehend its meaning.

\\U uppercase till \\E

\\E end case modification

Please give an example of the correct usage if possible and how to approach for a python equivalent.

Answer 1

The regex engine knows nothing of \\U . It's processed by the Perl parser in double quoted and regex literals.

"\Uabcdef"       is the same as     uc("abcdef")
"\Uabc\Edef"     is the same as     uc("abc")."def"

That means that

/^\Uabc/         is the same as     /^ABC/
/^\U/            is the same as     /^/

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/^/ (and thus /^\\U/ ) is rather pointless, as it will always match.

If you wanted to make sure a string consists entirely of upper case letters, you'd use /^\\p{Lu}*\\z/ , or /^[AZ]*\\z/ if you have a very limited definition of letter.

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Perl's

$var =~ /\Uabc\Edef/

would be written as follows in Python:

re.search("abc".upper() + "def", var)