Parsing: nws yog dab tsi thiab yuav ua li cas nws yog tsim

Heev feem ntau nyob rau hauv Internet, tej zaum koj yuav pom me ntsis ib lub sij hawm xws li "parsing". Yuav ua li cas yog nws thiab yog vim li cas koj yuav tsum? Nws thiaj li tshwm sim hais tias programmers muab txoj hauj lwm Spars kev kawm ntawv. Los yog ib tug ib txwm neeg siv yog ntsib nrog xws li ib tug lub sij hawm tsis paub nws tus nqi.

txhais

Yog hais tias peb coj ib tug kev txiav txim zoo, lub parsing - ib theem ntawm cov lus thaum muab piv nrog linear cai ntawm yam lus uas yuav ua tau tej yam tib neeg, siv nyob rau hauv kev sib txuas lus. Nws kuj yuav muaj kev hais lus, xws li hom lus programming.

Thiab nrog kev xav txog mus rau qhov chaw nyob rau hauv cov lus teb rau ib lo lus nug txog parsing - "nws yog dab tsi", "yog vim li cas siv" - nws yuav tau hais tias qhov no txheej txheem ntawm successive parsing ntawm cov ntaub ntawv uas yog muaj nyob rau ntawm nplooj ntawv Web site. Cov ntawv nyeem ntawm no yog ib tug txheej ntawm cov ntaub ntawv uas yog hierarchically kom thiab cob los ntawm txoj kev computer thiab tib neeg lus. Cov yav tas muab tso nyiaj ncaj qha ntaub ntawv, rau uas cov neeg thiab tuaj. Thiab programming lus qhia kom meej yuav ua li cas tso saib no cov ntaub ntawv rau tus neeg siv lub monitor.

cov ntsiab lus Nrhiav

Thaum tus tswv tsev tsuas tsim nws tus kheej lub site, nws kuj ntsib ib qho teeb meem: qhov twg kom tau cov ntsiab lus mus sau? Qhov zoo tshaj plaws kev xaiv yog mus nrhiav rau lub WAN. Tom qab tag nrho, muaj infinitely ntau kev txawj ntse. Tab sis, ces muaj yog ib co teeb meem:

• Txij li thaum lub internet yog tas li loj hlob thiab kev loj hlob, nws yog tseeb hais tias cov kawm ntawv yuav tsum muaj loj heev lawm ntawm cov ntaub ntawv nyob rau hauv thiaj li yuav muaj ib tug kom zoo dua li cov kev sib tw. Niaj hnub no, cov ntsiab lus muaj yuav heev npaum li cas. Ib tug manually sau nyob rau hauv raws li ntau qhov chaw cov ntaub ntawv yog heev yooj yim.
• Txij li thaum cov neeg tsis muaj peev xwm mus ua hauj lwm kev txom kwj ntawm puas tau-hloov ntaub ntawv yuav tsum parsing. Yuav ua li cas yuav nws muab? Automated ntaub ntawv sau ua ke thiab cov txheej txheem kev hloov.

pros parser

Ib tug kev pab cuam uas ua ib tug txheej txheem ntawm parsing, nyob rau hauv kev sib piv nrog ib tug neeg muaj ib tug xov tooj ntawm zoo:

• Nws sai sai taug kev los ntawm txhiab ntawm nplooj ntawv Web site.
• Tsis muaj teeb meem yuav muab kev cov ntaub ntawv thiab cov ntaub ntawv rau tus neeg txoj kev.
• Tsis muaj kev ua yuam kev muab pov tseg ruaj, tawm hauv xwb dab tsi yog tsim nyog.
• Tsim ntim cov ntaub ntawv tsim nyog rau tus neeg siv saib.

Ntawm cov hoob kawm, zaum kawg tshwm sim yuav tseem xav tau ib co kev kho mob. Nws tsis tseem ceeb rau ib tug spreadsheet los yog database. Tab sis qhov no yog yooj yim npaum li hais tias koj ua manually, es siv lub parsing. Yuav ua li cas nws ua li, nws yog tseeb - txuag lub sij hawm thiab kev rau siab.

tsim

ib tug ntau yam ntawm programming lus siv los tsim parsers. Cov feem ntau yog scripting lus. Qhov no txhais tau tias lawv sau nyob rau hauv tsab ntawv. Yuav ua li cas yog ib tsab ntawv thiab dab tsi yog parsing ua siv xws cov lus yuav muab suav hais tias tom qab.

Creation ntawm qhov kev pab cuam parser tsis yuav tsum tau tseem ceeb paub txog hom lus programming. Tsis teb los tau thiab cov ntaub ntawv hais txog cov technology. Tab sis ib yam dab tsi kom paub nws yog tseem tsim nyog. Yog li ntawd, yuav tsum paub yuav ua li cas los tsim parsing, uas yog, qhov kev pab cuam analyzer, koj yuav tsum paub cov nram qab no:

• Rau thawj zaug kev pab cuam lag luam algorithm xav tau ib tug meej tsom xam ntawm lub qhov code, web pages, uas yog ib tug neeg. Muaj tsis tau tsis muaj tsawg kawg yog nruab nrab kev txawj ntse ntawm typesetting tshuab. Qhov no HTML, CSS thiab JavaScript lus.
• Mus dhia dej ntxaum mus rau hauv cov kev kawm, koj yuav tsum paub ib tug technology hu ua dom. Nws muab ib lub sij hawm mus ua hauj lwm zoo heev los ntawm ib tug web page hierarchy.
• Cov feem ntau cov theem - sau ntawv ib parser. Ntawm no nws yog tsim nyog los muaj ib lub cuab tam rau cov zauv ntawv nyeem. Cov programmers feem ntau siv rau lub hom phiaj no, cov kab zauv, uas muaj hwj chim txaus. Tab sis nws yog ib lub zog yog tsis txhua tsim tawm. Ntawm no koj xav tau ib tug tshwj xeeb mindset. Cov pom cov tshuaj no yog siv ib tug npaj txhij-ua cov tsev qiv ntawv uas tau tsim rau cov parsing. Yuav ua li cas yog no cov tsev qiv ntawv? Nws yog packed nrog qhov kev pab cuam code, uas twb muaj tag nrho cov kev khiav dej num rau kev tsom xam.
• Nws yog ib co ntshaw kom to taub tus kwv-taw qhia kom paub programming, uas yog txaus siab los ntawm tej yam programming lus.
• Cov theem kawg yuav tus tsom xam ntawm cov kev tshwm sim ntawm cov zauv cov ntaub ntawv yuav tsum tau xyaum thiab khaws cia. Muaj tsis tau ua tsis paub txog ntawm databases.
• Peb yuav tsum tau paub thiab muaj lub zog tsim kev ua hauj lwm nrog cov ntaub ntawv. Tom qab tag nrho, cov ntaub ntawv yuav tsum tau sau ntawv mus rau cov tib cov ntaub ntawv, thiab ces, tej zaum, yuav hloov dua siab tshiab rau hauv ib tug spreadsheet cov hom ntawv.

theem

Yog hais tias tag nrho cov kev cai no yog tau ntsib, lub tom ntej cov txheej txheem yuav tsum tau muab faib mus rau hauv theem:

1. Nyob rau hauv thawj theem ntawm parsing tau qhov code nplooj ntawv Web site.
2. Cov kauj ruam tom ntej - extracting qhov tsim nyog cov ntaub ntawv los ntawm lub markup. Muaj pov tseg ruaj code, cov ntaub ntawv yog lub koom haum raws li lub hierarchy.
3. Tom qab kev vam meej cov ntaub ntawv yuav tsum tau muab cia rau hauv ib daim ntawv uas muaj peev xwm yuav ntxiv ua.
4. Txij li thaum lub qhov chaw tsis muaj ib tug tib page, thiab los ntawm lub teeb, lub algorithm yuav tsum tau tsiv mus nyob rau nplooj ntawv tom ntej.

Yog li ntawd, parsing - yog dab tsi? Qhov no yog tus txheej txheem ntawm cais site ntsiab lus thiab cais cov yam ntaub ntawv. Siv cov saum toj no, nws tseem tau mus sau lawv qhov chaw ib tug ntau ntawm cov ntsiab lus txiav. Qhov no ua rau nws tau mus yeej lub sij hawm thiab yeej tsis yooj yim kev sib tw nyob rau hauv kev ua lag luam saytostroiteley.