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George Burdell wrote:
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cite="mid:b0a74686-5f27-459b-84d3-8eef55ed9e01@m11g2000yqf.googlegroups.com"
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<pre wrap="">On Sep 6, 10:06 pm, "Mark Tolonen" <a class="moz-txt-link-rfc2396E" href="mailto:metolone+gm...@gmail.com"><metolone+gm...@gmail.com></a> wrote:
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<pre wrap=""><a class="moz-txt-link-rfc2396E" href="mailto:gburde...@gmail.com"><gburde...@gmail.com></a> wrote in message
<a class="moz-txt-link-freetext" href="news:f98a6057-c35f-4843-9efb-7f36b05b677c@g19g2000yqo.googlegroups.com">news:f98a6057-c35f-4843-9efb-7f36b05b677c@g19g2000yqo.googlegroups.com</a>...
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<pre wrap="">If I do this:
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<pre wrap="">import re
a=re.search(r'hello.*?money', 'hello how are you hello funny money')
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<pre wrap="">I would expect a.group(0) to be "hello funny money", since .*? is a
non-greedy match. But instead, I get the whole sentence, "hello how
are you hello funny money".
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<pre wrap="">Is this expected behavior? How can I specify the correct regexp so
that I get "hello funny money" ?
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<pre wrap="">A non-greedy match matches the fewest characters before matching the text
*after* the non-greedy match. For example:
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<pre wrap="">import re
a=re.search(r'hello.*?money','hello how are you hello funny money and
more money')
a.group(0) # non-greedy stops at the first money
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<pre wrap="">'hello how are you hello funny money'>>> a=re.search(r'hello.*money','hello how are you hello funny money and
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<pre wrap="">more money')
a.group(0) # greedy keeps going to the last money
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<pre wrap="">'hello how are you hello funny money and more money'
This is why it is difficult to use regular expressions to match nested
objects like parentheses or XML tags. In your case you'll need something
extra to not match the first hello.
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<pre wrap="">a=re.search(r'(?<!^)hello.*?money','hello how are you hello funny
money')
a.group(0)
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<pre wrap="">'hello funny money'
-Mark
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<pre wrap=""><!---->
I see now. I also understand r's response. But what if there are many
"hello"'s before "money," and I don't know how many there are? In
other words, I want to find every occurrence of "money," and for each
occurrence, I want to scan back to the first occurrence of "hello."
How can this be done?
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<br>
This is asking for more power then regular expressions can support.<br>
<br>
However, your request reads like an algorithm. Search for an
occurrence of "hello" (using the find string method), and search
backwards from there for "money" (use rfind string method). Two lines
of code in a loop should do it.<br>
<br>
<br>
Gary Herron<br>
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