[issue1633953] re.compile("(.*$){1,4}", re.MULTILINE) fails

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Fixed in issue2537. See also issue18647.

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nosy: +serhiy.storchaka
resolution:  -> duplicate
stage:  -> committed/rejected
status: open -> closed
superseder:  -> re.compile(r'((x|y+)*)*') should fail

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[issue1633953] re.compile("(.*$){1,4}", re.MULTILINE) fails

[Mark Lawrence]

Mark Lawrence  added the comment:

Can this be closed as a duplicate of #2537?

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nosy: +BreamoreBoy

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[issue1633953] re.compile("(.*$){1,4}", re.MULTILINE) fails

[Jeffrey C. Jacobs]

Jeffrey C. Jacobs <[EMAIL PROTECTED]> added the comment:

On first blush, this issue sounds quite similar to issue 2537, but I 
have been looking at different scenarios and found that there is a 
subtle difference because, grammatically:

(?m)(?:.*$)(.*$)

is the same as:

(?m)(.*$){2}

Yet the former compiles while the later raises the exception you list 
below.  Thus, I think the issue YOU raise is indeed related to the 
redundant repeat operator issue numbered 2537, BUT, when I match an 
expression with the alternate form, I get an empty string in my capture 
group, since in a range repeat over a capture group, only the last group 
is captured, while the entire expression matches only the first line, 
without the end-line character.  Thus, the other thing to remember is 
that ^ and $ are zero-width matches, so when you write .*$, you are 
saying match up to, but not including, the end of the line.  If you 
immediately follow that with another .*$, you will start from the point 
"up to, but not including, the end of the line", which means the next 
character is an end of line.  Thus, when you reach the second .*$, you 
capture nothing because the .* is allowed to be zero-length and you 
still haven't advanced PAST the end of the line.

As a working alternative, you could write r'(?m)(?:(.*$)[\r\n]*){1,4}' , 
since this would give you your 1-4 lines, but also consume the carriage 
return and line feed characters to get you to the next line.

Since we don't want to change the meaning of $ and ^ to make them 
capturing (custom POSIX character classes may make 'capturing' a new 
line character easier), and the 'redundant repeat operator' is already 
listed as a bug (your expression is essentially saying (.*){1,4}$ 
because it does not capture the new-line character(s) and thus has a 
redundant repeat operation in the range repeat expression), I'm willing 
to call this a repeat (technically repeated by as this issue is older) 
of issue 2537.

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[issue1633953] re.compile("(.*$){1,4}", re.MULTILINE) fails

[Jeffrey C. Jacobs]

Changes by Jeffrey C. Jacobs <[EMAIL PROTECTED]>:


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nosy: +timehorse
versions: +Python 2.7 -Python 2.5

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[issue1633953] re.compile("(.*$){1,4}", re.MULTILINE) fails

[Ralf Schmitt]

Changes by Ralf Schmitt:


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