lets say I have the phrase :
www w w w wwwcom com c o m
I want to block www, w w w com (when its not part of another word) and c o m
I can do this by looking for each of the following:
www
\bw w w\b
\bcom\b
\bc o m\b
However can i combine them into single statements that would search for both www and w w w or com and c o m leaving 2 regular expressions rather than 4?
You can use pipe to or your regex. For example rega|regb. In your case it will be:
\b((www)|(w w w))\b
Strip the white space as part of the match:
www - \b\s*w\s*w\s*w\s*\b
com - \b\s*c\s*o\s*m\s*\b
both - \b\s*w\s*w\s*w\s*|\s*c\s*o\s*m\s*\b
Sabuj Hassan's answer is the only way to get precisely what you've specified. However, if you're okay with also matching ww w and w ww, then you could use:
\bw ?w ?w\b
This will allow up to one space between each pair of letters (tabs, multiple spaces, etc will not be matched).
The same can be done for com. You can combine this with the | approach to get one regex:
\b(w ?w ?w|c ?o ?m)\b
David Haney's answer (using \s*) is similar, but will match "phrases" that have any combination of spaces and tabs between letters. For instance, w\t\t\t \tw w (where \t is a tab character) will be considered a match.
\b(w\s*w\s*w|c\s*o\s*m)\b
This matches:
www
com
ww w
co m
w w w
c o m
in:
www.something => matches www
wwwword => no matches
word.com => matches com
wordcom => no matches
doesn't match:
wwwe
ewww
come
ecom
Related
I am trying to figure out a regex. That includes all characters after it but if another patterns occurs it does not overlap
This is my current regex
[a-zA-Z]{2}\d{1}\s?\w?
The pattern is always 2 letter followed by a number like AE1 or BE3 but I need all the characters following the pattern.
So AE1 A E F but if another pattern occurs in the string like
AE1 A D BE1 A D C it cannot overlap with and be two separate matches.
So to clarify
AB3 D T B should be one match on the regex
ABC D A F DE3 D CD A
should have 2 matches with all the char following it because of the the two letter word and number.
How do I achieve this
I'm not quite following the logic here, yet my guess would be that we might want something similar to this:
([A-Z]{2}\d\s([A-Z]+\s)+)|([A-Z]{3}\s([A-Z]+\s)+)
which allows two letters followed by a digit, or three letters, both followed by ([A-Z]+\s)+.
Demo
Look, you have to consider where your pattern will start. I mean, you know, what is different between AE1 A E F and BE1 A D C in AE1 A D BE1 A D C? You don't want to treat both similarly. So you have to separate them. Separation of these two texts is possible only determining which one is placed in text start.
Altogether, only adding ^ to start your pattern will solve problem.
So your regex should be like this:
^[a-zA-Z]{2}\d{1}\s?\w?
Demo
What you want to do is to split a string with your pattern having the current pattern match as the start of the extracted substrings.
You may use
(?!^)(?=[a-zA-Z]{2}\d)
to split the string. Details
(?!^) - not at the start of the string
(?=[a-zA-Z]{2}\d) - a location in the string that is immediately followed with 2 ASCII letters and any digit.
See the Scala demo:
val s = "ABC D A F DE3 D CD A"
val rx = """(?!^)(?=[a-zA-Z]{2}\d)"""
val results = s.split(rx).map(_.trim)
println(results.mkString(", "))
// => ABC D A F, DE3 D CD A
You can just use this regex:
(?i)\b[a-z]{2}\d\b(?:(?:(?!\b[a-z]{2}\d\b).)+\s?)?
Demo and explanations: https://regex101.com/r/DtFU8j/1/
It uses a negative lookahead (?!\b[a-z]{2}\d\b) to add the constraint that the character matched after the initial pattern (?i)\b[a-z]{2}\d\b should not contain this exact pattern.
In the course of processing a large textual chemical database with Perl, I had been faced with the problem of using a regex to match chemical formulae. I have seen these two previous topics, but the suggested answers there are too loose for my requirements.
Specifically, my (admittedly limited) research has led me to this posting that gives a regex for the currently accepted chemical symbols, which I'll copy here for reference
[BCFHIKNOPSUVWY]|[ISZ][nr]|[ACELP][ru]|A[cglmst]|B[aehikr]|C[adeflos]|D[bsy]|Es|F[elmr]|G[ade]|H[efgos]|Kr|L[aiv]|M[cdgnot]|N[abdehiop]|O[gs]|P[abdmot]|R[abe-hnu]|S[bcegim]|T[abcehilms]|Xe|Yb
(Thus e.g. C, Cm, and Cn will pass, but not Cg or Cx.)
As with the previous questions, I also need to match numbers, complete sets of parentheses and complete sets of square brackets, so that both e.g. C2H6O and (CH3)2CFCOO(CH2)2Si(CH3)2Cl are matched.
So how do I combine the previous solutions with the grand regex for matching valid chemical elements to strictly match a chemical formula?
(If it's not too much trouble to add, a blow-by-blow account of how to humanly parse the regex would be appreciated greatly, though not strictly necessary.)
Brief
I decided why not create a massive regex to do what you want (but still maintain a clean regex). This regex would be used in conjunction with a loop to go over matches for bracket or parentheses groups.
Assumptions
I am assuming the following since the OP has not given a full list of positive and negative matches:
Nested parentheses aren't possible
Nested square brackets aren't possible
Square bracket groups that surround a single parentheses group are redundant and therefore incorrect
Square bracket groups must contain at least 2 groups, of which 1 such group must be a parentheses group
If any of these assumptions are incorrect, please let me know so that I may fix the regex accordingly
Answer
View this regex in use here
Code
(?(DEFINE)
(?# Periodic elements )
(?<Hydrogen>H)
(?<Helium>He)
(?<Lithium>Li)
(?<Beryllium>Be)
(?<Boron>B)
(?<Carbon>C)
(?<Nitrogen>N)
(?<Oxygen>O)
(?<Fluorine>F)
(?<Neon>Ne)
(?<Sodium>Na)
(?<Magnesium>Mg)
(?<Aluminum>Al)
(?<Silicon>Si)
(?<Phosphorus>P)
(?<Sulfur>S)
(?<Chlorine>Cl)
(?<Argon>Ar)
(?<Potassium>K)
(?<Calcium>Ca)
(?<Scandium>Sc)
(?<Titanium>Ti)
(?<Vanadium>V)
(?<Chromium>Cr)
(?<Manganese>Mn)
(?<Iron>Fe)
(?<Cobalt>Co)
(?<Nickel>Ni)
(?<Copper>Cu)
(?<Zinc>Zn)
(?<Gallium>Ga)
(?<Germanium>Ge)
(?<Arsenic>As)
(?<Selenium>Se)
(?<Bromine>Br)
(?<Krypton>Kr)
(?<Rubidium>Rb)
(?<Strontium>Sr)
(?<Yttrium>Y)
(?<Zirconium>Zr)
(?<Niobium>Nb)
(?<Molybdenum>Mo)
(?<Technetium>Tc)
(?<Ruthenium>Ru)
(?<Rhodium>Rh)
(?<Palladium>Pd)
(?<Silver>Ag)
(?<Cadmium>Cd)
(?<Indium>In)
(?<Tin>Sn)
(?<Antimony>Sb)
(?<Tellurium>Te)
(?<Iodine>I)
(?<Xenon>Xe)
(?<Cesium>Cs)
(?<Barium>Ba)
(?<Lanthanum>La)
(?<Cerium>Ce)
(?<Praseodymium>Pr)
(?<Neodymium>Nd)
(?<Promethium>Pm)
(?<Samarium>Sm)
(?<Europium>Eu)
(?<Gadolinium>Gd)
(?<Terbium>Tb)
(?<Dysprosium>Dy)
(?<Holmium>Ho)
(?<Erbium>Er)
(?<Thulium>Tm)
(?<Ytterbium>Yb)
(?<Lutetium>Lu)
(?<Hafnium>Hf)
(?<Tantalum>Ta)
(?<Tungsten>W)
(?<Rhenium>Re)
(?<Osmium>Os)
(?<Iridium>Ir)
(?<Platinum>Pt)
(?<Gold>Au)
(?<Mercury>Hg)
(?<Thallium>Tl)
(?<Lead>Pb)
(?<Bismuth>Bi)
(?<Polonium>Po)
(?<Astatine>At)
(?<Radon>Rn)
(?<Francium>Fr)
(?<Radium>Ra)
(?<Actinium>Ac)
(?<Thorium>Th)
(?<Protactinium>Pa)
(?<Uranium>U)
(?<Neptunium>Np)
(?<Plutonium>Pu)
(?<Americium>Am)
(?<Curium>Cm)
(?<Berkelium>Bk)
(?<Californium>Cf)
(?<Einsteinium>Es)
(?<Fermium>Fm)
(?<Mendelevium>Md)
(?<Nobelium>No)
(?<Lawrencium>Lr)
(?<Rutherfordium>Rf)
(?<Dubnium>Db)
(?<Seaborgium>Sg)
(?<Bohrium>Bh)
(?<Hassium>Hs)
(?<Meitnerium>Mt)
(?<Darmstadtium>Ds)
(?<Roentgenium>Rg)
(?<Copernicium>Cn)
(?<Nihonium>Nh)
(?<Flerovium>Fl)
(?<Moscovium>Mc)
(?<Livermorium>Lv)
(?<Tennessine>Ts)
(?<Oganesson>Og)
(?# Regex )
(?<Element>(?&Actinium)|(?&Silver)|(?&Aluminum)|(?&Americium)|(?&Argon)|(?&Arsenic)|(?&Astatine)|(?&Gold)|(?&Barium)|(?&Beryllium)|(?&Bohrium)|(?&Bismuth)|(?&Berkelium)|(?&Bromine)|(?&Boron)|(?&Calcium)|(?&Cadmium)|(?&Cerium)|(?&Californium)|(?&Chlorine)|(?&Curium)|(?&Copernicium)|(?&Cobalt)|(?&Chromium)|(?&Cesium)|(?&Copper)|(?&Carbon)|(?&Dubnium)|(?&Darmstadtium)|(?&Dysprosium)|(?&Erbium)|(?&Einsteinium)|(?&Europium)|(?&Iron)|(?&Flerovium)|(?&Fermium)|(?&Francium)|(?&Fluorine)|(?&Gallium)|(?&Gadolinium)|(?&Germanium)|(?&Helium)|(?&Hafnium)|(?&Mercury)|(?&Holmium)|(?&Hassium)|(?&Hydrogen)|(?&Indium)|(?&Iridium)|(?&Iodine)|(?&Krypton)|(?&Potassium)|(?&Lanthanum)|(?&Lithium)|(?&Lawrencium)|(?&Lutetium)|(?&Livermorium)|(?&Moscovium)|(?&Mendelevium)|(?&Magnesium)|(?&Manganese)|(?&Molybdenum)|(?&Meitnerium)|(?&Sodium)|(?&Niobium)|(?&Neodymium)|(?&Neon)|(?&Nihonium)|(?&Nickel)|(?&Nobelium)|(?&Neptunium)|(?&Nitrogen)|(?&Oganesson)|(?&Osmium)|(?&Oxygen)|(?&Protactinium)|(?&Lead)|(?&Palladium)|(?&Promethium)|(?&Polonium)|(?&Praseodymium)|(?&Platinum)|(?&Plutonium)|(?&Phosphorus)|(?&Radium)|(?&Rubidium)|(?&Rhenium)|(?&Rutherfordium)|(?&Roentgenium)|(?&Rhodium)|(?&Radon)|(?&Ruthenium)|(?&Antimony)|(?&Scandium)|(?&Selenium)|(?&Seaborgium)|(?&Silicon)|(?&Samarium)|(?&Tin)|(?&Strontium)|(?&Sulfur)|(?&Tantalum)|(?&Terbium)|(?&Technetium)|(?&Tellurium)|(?&Thorium)|(?&Titanium)|(?&Thallium)|(?&Thulium)|(?&Tennessine)|(?&Uranium)|(?&Vanadium)|(?&Tungsten)|(?&Xenon)|(?&Ytterbium)|(?&Yttrium)|(?&Zirconium)|(?&Zinc))
(?<Num>(?:[1-9]\d*)?)
(?<ElementGroup>(?:(?&Element)(?&Num))+)
(?<ElementParenthesesGroup>\((?&ElementGroup)+\)(?&Num))
(?<ElementSquareBracketGroup>\[(?:(?:(?&ElementParenthesesGroup)(?:(?&ElementGroup)|(?&ElementParenthesesGroup))+)|(?:(?:(?&ElementGroup)|(?&ElementParenthesesGroup))+(?&ElementParenthesesGroup)))\](?&Num))
)
^((?<Brackets>(?&ElementSquareBracketGroup))|(?<Parentheses>(?&ElementParenthesesGroup))|(?<Group>(?&ElementGroup)))+$
Explanation
The first part of the (?(DEFINE)) section lists each periodic element (ordered by atomic number for easy lookup).
The Element group acts as a simple or | between each of the elements listed in 1. ensuring that each element's symbol is ordered alphabetically by the first character, and then by symbol character length (so as not to catch, for example, Carbon C instead of Calcium Ca)
ElementGroup specifies a group of chemicals in the format: one or more Element followed by zero or more digits, excluding zero (specified by the group Num)
Valid Examples
C - Element
CH - Element followed by another Element
CH3 -Element followed by another Element and a Num
O2 - Element followed by a Num
Invalid Examples
N0 - 0 cannot be used explicitly
N01 - Num group specifies the number must begin with 1-9 or not have a number
A - Element does not exist
c - Element does not exist - case sensitive regex
ElementParenthesesGroup specifies one or more groupings of ElementGroup between parentheses ( ) but containing at least one ElementGroup
Valid Examples
(CH) - ElementGroup surrounded by parentheses
(CH3) - ElementGroup surrounded by parentheses
(CH3NO4) - multiple ElementGroup surrounded by parentheses
(CH3N04)2 - multiple ElementGroup surrounded by parentheses followed by a Num
Invalid Examples
(CH[NO4]) - Only ElementGroup is valid inside ElementParenthesesGroup
ElementSquareBracketGroup specifies a grouping of ElementParenthesesGroup or ElementGroup between square brackets [ ] but containing at least one ElementParenthesesGroup and one other group (ElementParenthesesGroup or ElementGroup)
Valid Examples
[CH3(NO4)] - Contains at least one ElementParenthesesGroup and one other ElementParenthesesGroup or ElementGroup
[(NO4)CH]2 - Contains at least one ElementParenthesesGroup and one other ElementParenthesesGroup or ElementGroup followed by Num
[(NO4)(CH3)] - Contains at least one ElementParenthesesGroup and one other ElementParenthesesGroup or ElementGroup
Invalid Examples
[(NO4)] - Does not contain second group, brackets [ ] are redundant
[NO4] - Does not contain ElementParenthesesGroup
Additional Information
I realize this is a very long answer, but the OP is asking a very specific question and wants to ensure specific criteria are met.
Ensure the following flags are set:
g - ensures global matches
x - ensures whitespace is ignored
if the data is across multiple lines (separated by a newline character) use m for multi line
Note: Regex will only capture the last group of type X that it finds (and overwrite the previously captured group of said type X. This is the default behaviour of regex and there is no way to currently override this behaviour. This may give you undesirable results. You can see this with the last example in the linked regex as well as with your example of (CH3)2CFCOO(CH2)2Si(CH3)2Cl since there are multiple of each group type.
It is best not to assemble such a large regex manually. Instead, let's assume we have an array of atoms #atoms. We can then create a regex matching any of these atoms like:
my ($atoms_regex) = map qr/$_/, join '|', map quotemeta, sort #atoms;
(Sort all items so that shorter atom names come first, then escape all items with quotemeta, join them with a | for alternatives, and compile the regex.)
You can add any used abbreviations to the #atoms array.
Next, we can write a regex that allows grouping and numbering. Our regex will match any number of items, where an item may be an atom or a group, and may be followed by a number:
my $chemical_formula_regex = qr/
(?&item)++
(?(DEFINE)
(?<item> (?: \((?&item)++\) | \[(?&item)++\] | $atoms_regex ) [0-9]* )
)
/x;
Within the (?(DEFINE) ...) group we can define named subpatterns with (?<name> ...). A subpattern is like a subroutine for a regex. We can call those subpatterns with (?&name). This allows us to structure the regex without unnecessary repetition.
The /x flag allows us to use whitespace and linebreaks and comments to lay out the regex in a more readable fashion. Regexes don't have to be an incomprehensible mess!
The ++ quantifier instead of + is not strictly necessary, but prevents unwanted backtracking. That may be a bit faster when a match fails.
Since this post is a top result for "regex chemistry symbols", I would also like to submit a solution. It is a python script that uses a regex to match chemistry formulas of the type A#B#, where A and B are chemical symbols and # is a number. The script as implemented matches and then surrounds the matches with \ce{} for use in LaTeX. It also includes the ability to exclude matches if the capture is in a user-defined list, which means words such as "I" and "In" will not be matched. Gist Link.
#!/usr/bin/env python3
# Find chemical symbols and surround them with \ce{ Symbol }
# Problem words: I, HOW, In, degrees K. Add words to exlist to ignore them.
import re, sys
if len(sys.argv) < 2 :
print('Usage:> {} <filename>'.format(sys.argv[0]))
sys.exit(1)
ptable =" H He "
ptable+=" Li Be B C N O F Ne "
ptable+=" Na Mg Al Si P S Cl Ar "
ptable+=" K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr "
ptable+=" Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe "
ptable+=" Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn "
ptable+=" Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og "
ptable+=" Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu "
ptable+=" Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr "
exlist = ['C','I','In','K','HOW'] # exclude these words from being replaced
orsyms = '|'.join(ptable.split())
resyms = re.compile(r'\b'+'((?:(?:{})\d*)+)'.format(orsyms)+r'\b')
latexfile=sys.argv[1]
with open(latexfile,'r') as fd:
for line in fd:
for m in list(set(resyms.findall(line))):
if m not in exlist :
line = re.sub(r'\b'+m+r'\b', r'\ce{'+m+r'}', line)
print(line,end='')
Trying to remove all characters except from the compination of 'r d`. To be more clear some examples:
a ball -> ball
r something -> something
d someone -> someone
r d something -> r d something
r something d -> something
Till now I managed to remove the letters except from r or d, but this is not what i want. I want to keep only the compination(ex.4). I use this:
\b(?!r|d)\w{1}\b
Any idea who to do it?
Edit:The reg engine supports lookbehinds.
You may capture the r d combination and use a backreference in the replacement pattern to restore that combination, and remove all other matches:
\b(r d)\b|\b\w\b\s*
See the regex demo (replace with $1 that will put the r d back into the result).
Details:
\b(r d)\b - a "whole word" r d that is captured into Group 1
| - or
\b\w\b\s* - a single whole word consisting of 1 letter/digit/underscore (\b\w\b) and followed with 0+ whitespaces (\s*, just for removing the excessive whitespace, might not be necessary).
I have a file full of URLs in a weird format, characters separated by a space character.
h t t p : / / w w w . y o u t u b e . c o m / u s e r / A S D
h t t p : / / m o r c c . c o m / f r m / i n d . p h p ? t o p i c = 5 7 . 0
I would like to make it look like :
http://www.youtube.com/user/ASD
http://morcc.com/frm/ind.php?topic=57.0
I use notepad++, and I think regex could take care of this problem for me, unfortunately I don't know regex.
I want to remove the ' ' character (space) between the characters, and leave them in listed format, so replacing /s with '' is not a solution, because it becomes a mess :/
I think I should also insert a /n BEFORE "http" occurs.
Can you not just replace a space ' ' with an empty string ''? Replacing \s is not working how you want because newlines are also matched.
If that doesn't work you could, as you say, replace \s with '' and then replace http with \nhttp.
Regex is fairly basic. Check out the examples page. The second example seems to have what you're looking for: http://www.regular-expressions.info/examples.html
EDIT: Also, I assume you know this, but just to be sure, regex itself will not do what you want. What language are you planning on using regex with, so that people can provide more detailed responses?
Regex reference page [Bookmark it ;)] - http://www.regular-expressions.info/reference.html
I have the following data:
a b c d FROM:<uniquepattern1>
e f g h TO:<uniquepattern2>
i j k l FROM:<uniquepattern1>
m n o p TO:<uniquepattern3>
q r s t FROM:<uniquepattern4>
u v w x TO:<uniquepattern5>
I would like a regex query that can find the contents of TO: when FROM:<uniquepattern1> is encountered, so the results would be uniquepattern2 and uniquepattern3.
I am hopeless with regex, I would appreciate any pointers on how to write this (lookahead parameters?) and any differences between regex on different platforms (eg the C# .NET Regex versus Grep vs Perl) that might be relevant here.
Thank you.
Try:
/FROM:<uniquepattern1>.*\r?\n.*?TO:<(.*?)>/
This works by first finding the FROM anchor and then use a dot wildcard. The dot operator does not match a newline so this will consume the rest of the line. A non-greedy dot wildcard match then consumes up to the next TO and captures what's between the angle brackets.
your requirement for file parsing is simple. there is no need to use regular expression. Open the file for reading, go through each line check for FROM:<uniquepattern1>, get the next line and print them out. Furthermore, your TO lines are only separated by ":". therefore you can use that as field delimiter.
eg with awk
$ awk -F":" '/FROM:<uniquepattern1>/{getline;print $2}' file
<uniquepattern2>
<uniquepattern3>
the same goes for other languages/tools