Predpogoj: Regularni izraz s primeri | Python
Regularni izraz (včasih imenovan tudi racionalni izraz) je zaporedje znakov, ki definirajo vzorec iskanja, predvsem za uporabo pri ujemanju vzorcev z nizi ali ujemanju nizov, tj. operacijah, podobnih iskanju in zamenjavi. Regularni izrazi so posplošen način za ujemanje vzorcev z zaporedji znakov.
Modul Regularni izrazi (RE) določa nabor nizov (vzorec), ki se ujema z njim. Da bi razumeli analogijo RE,MetaCharacters>so uporabni, pomembni in bodo uporabljeni v funkcijah modulare>.
Skupaj je 14 metaznakov in o njih bomo razpravljali, ko sledijo funkcijam:
Used to drop the special meaning of character following it (discussed below) [] Represent a character class ^ Matches the beginning $ Matches the end . Matches any character except newline ? Matches zero or one occurrence. | Means OR (Matches with any of the characters separated by it. * Any number of occurrences (including 0 occurrences) + One or more occurrences {} Indicate number of occurrences of a preceding RE to match. () Enclose a group of REs> re.search()
re.search()>vrne None (če se vzorec ne ujema) ali are.MatchObject>ki vsebuje informacije o ujemajočem se delu niza. Ta metoda se ustavi po prvem ujemanju, zato je bolj primerna za testiranje regularnega izraza kot za pridobivanje podatkov.
primer:
java celo število v niz
Python3
# A Python program to demonstrate working of re.match().> import> re> > # Lets use a regular expression to match a date string> # in the form of Month name followed by day number> regex>=> r>'([a-zA-Z]+) (d+)'> > match>=> re.search(regex,>'I was born on June 24'>)> > if> match !>=> None>:> > ># We reach here when the expression '([a-zA-Z]+) (d+)'> ># matches the date string.> > ># This will print [14, 21), since it matches at index 14> ># and ends at 21.> >print>(>'Match at index % s, % s'> %> (match.start(), match.end()))> > ># We us group() method to get all the matches and> ># captured groups. The groups contain the matched values.> ># In particular:> ># match.group(0) always returns the fully matched string> ># match.group(1) match.group(2), ... return the capture> ># groups in order from left to right in the input string> ># match.group() is equivalent to match.group(0)> > ># So this will print 'June 24'> >print>(>'Full match: % s'> %> (match.group(>0>)))> > ># So this will print 'June'> >print>(>'Month: % s'> %> (match.group(>1>)))> > ># So this will print '24'> >print>(>'Day: % s'> %> (match.group(>2>)))> > else>:> >print>(>'The regex pattern does not match.'>)> |
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Izhod:
Match at index 14, 21 Full match: June 24 Month: June Day: 24>
re.findall()
Vrni vsa neprekrivajoča se ujemanja vzorca v nizu kot seznam nizov. Niz se pregleda od leve proti desni in ujemanja se vrnejo v najdenem vrstnem redu.
primer:
Python3
# A Python program to demonstrate working of> # findall()> import> re> > # A sample text string where regular expression> # is searched.> string>=> '''Hello my Number is 123456789 and> >my friend's number is 987654321'''> > # A sample regular expression to find digits.> regex>=> 'd+'> > match>=> re.findall(regex, string)> print>(match)> |
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zemljevid v tipkopisu
Izhod:
['123456789', '987654321']>