python Programming Glossary: lookahead

Impossible lookbehind with a backreference

http://stackoverflow.com/questions/10279055/impossible-lookbehind-with-a-backreference

much better it also matches here as if it was a positive lookahead print re.sub r' . 1 ' r' g 0 ' test x A A A A Ay B B B Bz And..

Match exactly N repetitions of the same character

http://stackoverflow.com/questions/10319696/match-exactly-n-repetitions-of-the-same-character

regex perl share improve this question Use negative lookahead and negative lookbehind. This would be the regex . 1. 1 N 1..

Python/Regex - Match .#,#. in String

http://stackoverflow.com/questions/12608152/python-regex-match-in-string

question To allow for multiple consecutive matches use lookahead lookbehind r' . d d . ' Example re.findall r' . d d . ' 'Test7.5.. . d d . ' 'Test7.5 6.7 8.test' '5 6' '7 8' We can also use lookahead to perform the split as you want it import re def split_it s..

python re.split() to split by spaces, commas, and periods, but not in cases like 1,000 or 1.50

http://stackoverflow.com/questions/12683201/python-re-split-to-split-by-spaces-commas-and-periods-but-not-in-cases-like

regex share improve this question Use a negative lookahead and a negative lookbehind s one two 3.4 5 6 seven.eight nine..

Using lookahead with generators

http://stackoverflow.com/questions/1517862/using-lookahead-with-generators

lookahead with generators I have implemented a generator based scanner.. sequence of items at once but each item as needed makes lookaheads a bit trickier compared to lists since the next item is not.. a straightforward implementation of a generator based lookahead look like Currently I'm using a workaround which implies making..

Python/YACC: Resolving a shift/reduce conflict

http://stackoverflow.com/questions/2939888/python-yacc-resolving-a-shift-reduce-conflict

Your basic problem is that you need two tokens of lookahead to do what you want when the input seen so far is a course and.. you want when the input seen so far is a course and the lookahead is a OR_CONJ you don't know whether to reduce the course to.. any can deal with this. use a lexer hack to do the lookahead basically have the lexer return two different OR_CONJ tokens..

Efficient Context-Free Grammar parser, preferably Python-friendly

http://stackoverflow.com/questions/4543008/efficient-context-free-grammar-parser-preferably-python-friendly

going with a home brewed top down backtracking unlimited lookahead lexical analyzer and parser and spending the bulk of your time..

Find all occurrences of a substring in Python

http://stackoverflow.com/questions/4664850/find-all-occurrences-of-a-substring-in-python

test' 0 5 10 15 If you want to find overlapping matches lookahead will do that m.start for m in re.finditer ' tt ' 'ttt' 0 1 If.. all without overlaps you can combine positive and negative lookahead into an expression like this search 'tt' m.start for m in re.finditer..

Regex: How to match sequence of key-value pairs at end of string

http://stackoverflow.com/questions/5323703/regex-how-to-match-sequence-of-key-value-pairs-at-end-of-string

share improve this question The negative zero width lookahead is pattern . It's mentioned part way down the re module documentation.. ... Matches if ... doesn 脌 match next. This is a negative lookahead assertion. For example Isaac Asimov will match 'Isaac ' only..

Python regex find all overlapping matches?

http://stackoverflow.com/questions/5616822/python-regex-find-all-overlapping-matches

8912345678 9123456789 I've found references to a lookahead but the examples I've seen only show pairs of numbers rather..

Python - regex - Splitting string before word

http://stackoverflow.com/questions/6709067/python-regex-splitting-string-before-word

Arginine and proline metabolism' the ... group is a lookahead assertion the expression matches a space note the space at the..