łň 4ŇÇIc@sidZdZddkZddkZddkTdefd„ƒYZd„Zedjo eƒndS( sŔPorter Stemming Algorithm This is the Porter stemming algorithm, ported to Python from the version coded up in ANSI C by the author. It follows the algorithm presented in Porter, M. "An algorithm for suffix stripping." Program 14.3 (1980): 130-137. only differing from it at the points maked --DEPARTURE-- and --NEW-- below. For a more faithful version of the Porter algorithm, see http://www.tartarus.org/~martin/PorterStemmer/ Later additions: June 2000 The 'l' of the 'logi' -> 'log' rule is put with the stem, so that short stems like 'geo' 'theo' etc work like 'archaeo' 'philo' etc. This follows a suggestion of Barry Wilkins, reasearch student at Birmingham. February 2000 the cvc test for not dropping final -e now looks after vc at the beginning of a word, so are, eve, ice, ore, use keep final -e. In this test c is any consonant, including w, x and y. This extension was suggested by Chris Emerson. -fully -> -ful treated like -fulness -> -ful, and -tionally -> -tion treated like -tional -> -tion both in Step 2. These were suggested by Hiranmay Ghosh, of New Delhi. Invariants proceed, succeed, exceed. Also suggested by Hiranmay Ghosh. Additional modifications were made to incorperate this module into nltk. All such modifications are marked with "--NLTK--". The nltk version of this module is maintained by the NLTK developers, and is available from t plaintexti˙˙˙˙N(t*t PorterStemmercBsżeZdZd„Zd„Zd„Zd„Zd„Zd„Zd„Z d„Z d „Z d „Z d „Z d „Zd „Zd„Zd„Zded„Zd„Zd„Zd„ZRS(st A word stemmer based on the Porter stemming algorithm. Porter, M. "An algorithm for suffix stripping." Program 14.3 (1980): 130-137. A few minor modifications have been made to Porter's basic algorithm. See the source code of this module for more information. The Porter Stemmer requires that all tokens have string types. cCs d|_d|_d|_d|_hddgd<dgd<dgd<d gd <d gd <d d gd <ddgd<ddgd<dgd<dgd<dgd<dgd<}h|_x6|iƒD](}x||D]}||i| b[i] is a consonant.tatetitotuityi(RRtcons(RR$((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pyR(ŸsdcCsřd}|i}x:||ijo|Sn|i|ƒpPn|d}q|d}x›x:||ijo|Sn|i|ƒoPn|d}q\|d}|d}x:||ijo|Sn|i|ƒpPn|d}q­|d}qYdS(sNm() measures the number of consonant sequences between k0 and j. if c is a consonant sequence and v a vowel sequence, and <..> indicates arbitrary presence, gives 0 vc gives 1 vcvc gives 2 vcvcvc gives 3 .... iiN(RRR((RtnR$((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytmŞs2        cCs@x9t|i|idƒD]}|i|ƒpdSqqWdS(s2vowelinstem() is TRUE <=> k0,...j contains a vowelii(trangeRRR((RR$((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pyt vowelinstemĎs  cCsP||idjodSn|i||i|djodSn|i|ƒS(s:doublec(j) is TRUE <=> j,(j-1) contain a double consonant.ii(RRR((RR((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytdoublecÖs cCsĆ|djodSn|djo"|idƒ o |idƒSn|i|ƒ p)|i|dƒp|i|dƒ odSn|i|}|djp|djp |djodSndS(s˘cvc(i) is TRUE <=> a) ( --NEW--) i == 1, and p[0] p[1] is vowel consonant, or b) p[i - 2], p[i - 1], p[i] has the form consonant - vowel - consonant and also if the second c is not w, x or y. this is used when trying to restore an e at the end of a short word. e.g. cav(e), lov(e), hop(e), crim(e), but snow, box, tray. iiitwtxR'(R(R(RR$tch((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytcvcŢs /B 'cCs›t|ƒ}||d|i|ijodSn||i|idjodSn|i|i|d|id!|jodSn|i||_dS(s3ends(s) is TRUE <=> k0,...k ends with the string s.ii(tlenRRRR(Rtstlength((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytendsős )cCsQt|ƒ}|i|id ||i|i|d|_|i||_dS(sJsetto(s) sets (j+1),...k to the characters in the string s, readjusting k.iN(R2RRR(RR3R4((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytsettos 1cCs(|iƒdjo|i|ƒndS(sr(s) is used further down.iN(R*R6(RR3((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytrscCs†|i|idjoŸ|idƒo|id|_qś|idƒo8|idjo|id|_q˛|id|_qś|i|iddjo|id|_qśn|idƒo8|idjo|id|_q‚|id|_n…|idƒo+|iƒdjo|id|_q‚nJ|id ƒp|id ƒo)|iƒo|i|_|id ƒo|id ƒq‚|id ƒo|idƒq‚|idƒo|idƒq‚|i|iƒo_|id|_|i|i}|djp|djp |djo|id|_q~q‚|iƒdjo$|i|iƒo|idƒq‚ndS(sBstep1ab() gets rid of plurals and -ed or -ing. e.g. caresses -> caress ponies -> poni sties -> sti tie -> tie (--NEW--: see below) caress -> caress cats -> cat feed -> feed agreed -> agree disabled -> disable matting -> mat mating -> mate meeting -> meet milling -> mill messing -> mess meetings -> meet R3tssesitiesiitiedteedtedtingtattatetbltbletiztizetltzR#N( RRR5RR*R,R6R-R1(RR0((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytstep1ab s8- !!!'&cCsh|idƒoT|idjoD|i|idƒo-|i|i d|i|id|_ndS(sstep1c() turns terminal y to i when there is another vowel in the stem. --NEW--: This has been modified from the original Porter algorithm so that y->i is only done when y is preceded by a consonant, but not if the stem is only a single consonant, i.e. (*c and not c) Y -> I So 'happy' -> 'happi', but 'enjoy' -> 'enjoy' etc This is a much better rule. Formerly 'enjoy'->'enjoi' and 'enjoyment'-> 'enjoy'. Step 1c is perhaps done too soon; but with this modification that no longer really matters. Also, the removal of the vowelinstem(z) condition means that 'spy', 'fly', 'try' ... stem to 'spi', 'fli', 'tri' and conflate with 'spied', 'tried', 'flies' ... R'iiR$N(R5RR(RR(R((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytstep1cGs7cCs|i|iddjoF|idƒo|idƒq˙|idƒo|idƒq˙nŸ|i|iddjoF|idƒo|id ƒq˙|id ƒo|id ƒq˙n>|i|idd jo%|id ƒo|idƒq˙nţ|i|iddjoë|idƒo|idƒq˙|idƒo2|iƒdjo|idƒ|iƒqq˙|idƒo|idƒq˙|idƒo|idƒq˙|idƒo|id ƒq˙|idƒo|idƒq˙nř|i|iddjog|idƒo|idƒq˙|idƒo|idƒq˙|idƒo|idƒq˙nv|i|idd joˆ|id!ƒo|idƒq˙|id"ƒo|id#ƒq˙|id$ƒo|idƒq˙|id%ƒo|idƒq˙nÓ|i|idd&jog|id'ƒo|idƒq˙|id(ƒo|id#ƒq˙|id)ƒo|idƒq˙nQ|i|idd*jo5|id+ƒo!|id|_|id,ƒq˙nd-S(.słstep2() maps double suffices to single ones. so -ization ( = -ize plus -ation) maps to -ize etc. note that the string before the suffix must give m() > 0. iR"tationalR?ttionalttiontctencitencetancitanceR#tizerRCRDtbliRAtalliitaltfullitfultentlitenttelitouslitousR%tizationtationtatorR3talismtivenesstivetfulnesstousnesstttalititivititbilititgtlogitogN(RRR5R7R*R6tstep2R(R((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pyRj]sF!%!%%! !!!%!!%!!!%!!%cCsW|i|idjog|idƒo|idƒqS|idƒo|idƒqS|idƒo|idƒqSnÖ|i|idjo%|id ƒo|idƒqSnš|i|id joF|id ƒo|idƒqS|id ƒo|idƒqSn=|i|id jo%|idƒo|idƒqSndS(sDstep3() dels with -ic-, -full, -ness etc. similar strategy to step2.R#ticatetictativeRtalizeRSR$ticitiRDticalRUR3tnessN(RRR5R7(R((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytstep3‰s!!%%!%cCsy|i|iddjo|idƒoqRdSn|i|iddjo0|idƒoqR|idƒoqRdSnŃ|i|iddjo|id ƒoqRdSnš|i|idd jo|id ƒoqRdSnc|i|idd jo0|id ƒoqR|idƒoqRdSn|i|iddjoX|idƒoqR|idƒoqR|idƒoqR|idƒoqRdSnĽ|i|iddjo^|idƒo2|i|idjp|i|idjoqR|idƒoqRdSn,|i|iddjo|idƒoqRdSnő|i|iddjo0|idƒoqR|idƒoqRdSnŞ|i|iddjo|idƒoqRdSns|i|iddjo|idƒoqRdSn<|i|idd jo|id!ƒoqRdSndS|iƒdjo|i|_ndS("s:step4() takes off -ant, -ence etc., in context vcvc.iR"RSNRKRORMR#terR$RlRDtabletibleR)tanttementtmentRWR%tionR3RctoutismR?titiR&RZtvR`RERC(RRR5RR*(R((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytstep4—s\BcCsÎ|i|_|i|idjoV|iƒ}|djp%|djo,|i|idƒ o|id|_qyn|i|idjo:|i|iƒo'|iƒdjo|id|_ndS(sYstep5() removes a final -e if m() > 1, and changes -ll to -l if m() > 1. R#iRDN(RRRR*R1R-(RR"((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytstep5Ęs  2=icCsü|tjot|ƒd}n||_||_||_|ii|i|i|id!ƒo#|i|i|i|id!Sn|i|idjo |iSn|iƒ|iƒ|i ƒ|i ƒ|i ƒ|i ƒ|i|i|id!S(sńIn stem(p,i,j), p is a char pointer, and the string to be stemmed is from p[i] to p[j] inclusive. Typically i is zero and j is the offset to the last character of a string, (p[j+1] == ''). The stemmer adjusts the characters p[i] ... p[j] and returns the new end-point of the string, k. Stemming never increases word length, so i <= k <= j. To turn the stemmer into a module, declare 'stem' as extern, and delete the remainder of this file. i( tNoneR2RRRRthas_keyRFRGRjRrR~R(RtpR$R((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pyt stem_wordÖs    '#       cCsh|iƒ}d}xOtt|ƒƒD];}||||jo|||7}q%|||7}q%W|S(NR(tlowertxrangeR2(RtwordtstemR„tretR/((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pyt adjust_caseýs cCs5|i|iƒdt|ƒdƒ}|i||ƒS(Nii(RƒR„R2R‰(RR†R‡((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pyR‡s%cCsdS(Ns((R((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pyt__repr__$s(t__name__t __module__t__doc__R!R(R*R,R-R1R5R6R7RFRGRjRrR~RR€RƒR‰R‡RŠ(((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pyRVs( 8 %      ;  ,  3 ' ! c CsUddkl}ddkl}|iƒ}g}g}x[|iƒd D]I}x@|i|ƒD]/\}}|i|ƒ|i|i|ƒƒq_WqIWdi|ƒ}t i dd|dƒi ƒ}di|ƒ} t i dd| dƒi ƒ} di d ƒi dd ƒi d dƒGH| GHd i d ƒi dd ƒi d dƒGH|GHd d GHd S(s^ A demonstration of the porter stemmer on a sample from the Penn Treebank corpus. i˙˙˙˙(ttreebank(R‡it s (.{,70})\ss\1\ns -Original-iFRt-s -Results-N(t nltk.corpusRŽtnltkR‡Rtfilest tagged_wordstappendtjointretsubtrstriptcentertreplace( RŽR‡tstemmertorigtstemmedtitemR†ttagtresultstoriginal((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pytdemo8s(   &&t__main__( Rt __docformat__tsysR—tapitStemmerIRRŁR‹(((s&/p/zhu/06/nlp/nltk/nltk/stem/porter.pysIs   ˙ă #