2d:null 2e:["$","title",null,{"children":"Regular Expressions Guide | Giacomo Nanni | Observable"}] 33:T67d,--- ### Basic concepts:
**Boolean "or"** A vertical bar separates alternatives. For example, gray|grey can match "gray" or "grey". **Grouping** Parentheses are used to define the scope and precedence of the operators (among other uses). For example, gray|grey and gr(a|e)y are equivalent patterns which both describe the set of "gray" or "grey". **Quantification** A quantifier after an element (such as a token, character, or group) specifies how many times the preceding element is allowed to repeat. The most common quantifiers are the question mark `?`, the asterisk `*`, and the plus sign `+`. | | | |---------------|-----------| | ? | The question mark indicates zero or one occurrences of the preceding element. For example,colou?r matches both "color" and "colour". | | * | The asterisk indicates zero or more occurrences of the preceding element. For example, ab*c matches "ac", "abc", "abbc", "abbbc", and so on. | | + | The plus sign indicates one or more occurrences of the preceding element. For example, ab+c matches "abc", "abbc", "abbbc", and so on, but not "ac". | | {n} | The preceding item is matched exactly n times | | {min,} | The preceding item is matched min or more times. | | {,max} | The preceding item is matched up to max times. | | {min,max} | The preceding item is matched at least min times, but not more than max times.| --- #### References - [☞ wiki](https://en.wikipedia.org/wiki/Regular_expression) - [☞ regex101](https://regex101.com/)34:T56e,regexExamples1 = [ { regex: "Fox", description: "matches any string that has the text >fox< in it" }, { regex: "^The", description: "matches any string that starts with >The<" }, { regex: "dog.$", description: "matches a string that ends with >dog.<" }, { regex: "^The quick brown Fox jumps over the lazy dog.$", description: "exact string match (starts and ends with >The quick brown fox jumps over the lazy dog)<" }, { regex: "F.?x", description: "matches any string between the letter F and x" }, { regex: "F.+?r", description: "Matches any character one or more times included inside F and r, expanding as needed." }, { regex: "[Fox]", description: "Matches a string that has either a F, o, x" }, { regex: "\\w", description: "matches any word character" }, { regex: "\\s", description: "matches any white space character" }, { regex: "[a-zA-Z]", description: "literals only" }, { regex: "[a-z]", description: "Lowercase only" }, { regex: "[A-Z]", description: "Uppercase only" }, { regex: "[a-zA-Z]{5}", description: "Matches a string of 5 letters." }, { regex: "[a-zA-Z]{5}\\s[a-zA-Z]{3}\\s[a-zA-Z]{5}", description: "Matches a string of 5 letters followed by one of 3 and again another by 5." } ]35:T713,testText = ` April is the cruellest month, breeding Lilacs out of the dead land, mixing Memory and desire, stirring Dull roots with spring rain. Winter kept us warm, covering Earth in forgetful snow, feeding A little life with dried tubers. Summer surprised us, coming over the Starnbergersee With a shower of rain; we stopped in the colonnade, And went on in sunlight, into the Hofgarten, And drank coffee, and talked for an hour. Bin gar keine Russin, stamm’ aus Litauen, echt deutsch. And when we were children, staying at the arch-duke’s, My cousin’s, he took me out on a sled, And I was frightened. He said, Marie, Marie, hold on tight. And down we went. In the mountains, there you feel free. I read, much of the night, and go south in the winter. What are the roots that clutch, what branches grow Out of this stony rubbish? Son of man, You cannot say, or guess, for you know only A heap of broken images, where the sun beats, And the dead tree gives no shelter, the cricket no relief, And the dry stone no sound of water. Only There is shadow under this red rock, (Come in under the shadow of this red rock), And I will show you something different from either Your shadow at morning striding behind you Or your shadow at evening rising to meet you; I will show you fear in a handful of dust. Frisch weht der Wind Der Heimat zu Mein Irisch Kind, Wo weilest du? “You gave me hyacinths first a year ago; “They called me the hyacinth girl.” —Yet when we came back, late, from the Hyacinth garden, Your arms full, and your hair wet, I could not Speak, and my eyes failed, I was neither Living nor dead, and I knew nothing, Looking into the heart of light, the silence. Oed’ und leer das Meer.`36:[{"id":"f451547e0bc8cf550a2de24def6777099c59ea40a8831b6beaac2ee76fa9f75d751b35c08f0b6790ed65b5cedc76e8f2ec8ee699d94bd67d6cb35a9d0dd26432","href":"https://static.observableusercontent.com/files/f451547e0bc8cf550a2de24def6777099c59ea40a8831b6beaac2ee76fa9f75d751b35c08f0b6790ed65b5cedc76e8f2ec8ee699d94bd67d6cb35a9d0dd26432","name":"out 2.csv","type":"text/csv","lastModified":1664897636356.944,"size":1499336},{"id":"c861dce708133978da91470876a281f582a420717c315c5d6c4b4ed39723ce103dbd9dc047ee7f7c80cc58728adc4073e96b4edaedd5f3cf8b9d07d3b1ca38d0","href":"https://static.observableusercontent.com/files/c861dce708133978da91470876a281f582a420717c315c5d6c4b4ed39723ce103dbd9dc047ee7f7c80cc58728adc4073e96b4edaedd5f3cf8b9d07d3b1ca38d0","name":"Screenshot 2022-10-04 at 17.47.33.png","type":"image/png","lastModified":1664898459418.543,"size":83984},{"id":"07d82b23cac984268acfb8864f44696c42ba0a5ca1f54cc96be5085dd374eb90daf625d388a4d0c7d34dc917b8db51236da5ad2cad62783da24b394e19d00730","href":"https://static.observableusercontent.com/files/07d82b23cac984268acfb8864f44696c42ba0a5ca1f54cc96be5085dd374eb90daf625d388a4d0c7d34dc917b8db51236da5ad2cad62783da24b394e19d00730","name":"ost@2.txt","type":"text/plain","lastModified":1664895270010.762,"size":146071}] 31:{"id":"7111f534ccec1869","slug":"regular-expressions-guide","title":"Regular Expressions Guide","thumbnail":"ff163dc3c592754cadedca51f3dcdb096d3aaf9761111b73ff17718a66cf8b66","access_level":"public","create_time":"$D2022-09-26T11:24:33.630Z","update_time":"$D2022-10-06T07:45:04.492Z","view_time":null,"first_public_time":"$D2022-09-27T15:00:52.248Z","has_unpublished_edits":null,"fork":false,"stars":1,"starred":false,"owner":{"type":"team","id":"5129c2957f22f1f2","login":"sinanatra","name":"Giacomo Nanni","avatar_url":"https://avatars-next.observableusercontent.com/780b6bc6dd2a5bbb19911ff3ee47ff844b4e25436b3bd6a0cde359479c6b4dd9","tier":"starter_2024"},"version":990,"publish_version":990,"role":null,"authored":false,"authors":[{"type":"individual","id":"c9e695131ad6aff8","login":"sinanatra","name":"Giacomo Nanni","avatar_url":"https://avatars-next.observableusercontent.com/780b6bc6dd2a5bbb19911ff3ee47ff844b4e25436b3bd6a0cde359479c6b4dd9","tier":null}],"members":[{"type":"individual","id":"c9e695131ad6aff8","login":"sinanatra","name":"Giacomo Nanni","avatar_url":"https://avatars-next.observableusercontent.com/780b6bc6dd2a5bbb19911ff3ee47ff844b4e25436b3bd6a0cde359479c6b4dd9","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":true,"trashed":false,"lapsed":null,"subscribed":null,"forks":1,"collection":null,"type":"notebook","body":{"title":"Regular Expressions Guide","cells":[{"id":0,"value":"# Regular Expressions Guide","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":6,"value":"A regular expression (regex or regexp) is a sequence of characters which allow to extract information from any text, mainly through \"find\" or \"find and replace\" operations.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":808,"value":"___\nExample: Selecting all double spaces after a comma which are followed by a letter: \n`/,\\s{2}(?=[a-zA-Z])/g`","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":789,"value":"{\n const example = `Unreal City, \nUnder the brown fog of a winter dawn,\nA crowd flowed over London Bridge, so many,\nI had not thought death had undone so many.\nSighs, short and infrequent, were exhaled, \nAnd each man fixed his eyes before his feet.`;\n \n const highlite = example.replace(new RegExp(\"\\,\\\\s{2}(?=[a-zA-Z])\", 'g'), function (a, b) {\n return \"\" + a + \"\";\n }).replaceAll(\" \", \" \").replaceAll(\"\\n\",\"
\"); \n \n return html`

${highlite}

`;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":601,"value":"$33","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":592,"value":"---\n### Example 1","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":144,"value":"{\n const highlite = text1.replace(regex1, function (a, b) {\n return \"\" + a + \"\";\n });\n return html`

${highlite}

`;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":67,"value":"viewof regexTable1 = Inputs.table(regexExamples1, {\n multiple: false,\n value: regexExamples1[0]\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":595,"value":"---\n### Example 2","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":408,"value":"{\n const highlite = text2.replaceAll(\" \",\" \").replaceAll(\"\\n\",\"
\").replace(regex2, function (a, b) {\n return \"\" + a + \"\";\n });\n return html`

${highlite}

`;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":427,"value":"viewof regexTable2 = Inputs.table(regexExamples2, {\n multiple: false,\n value: regexExamples2[0]\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":954,"value":"

\n---\n### Actually, search a lot on [☞ Stack Overflow](https://stackoverflow.com/questions/tagged/regex)\n\n\n

There are more than 250.000 questions asked regarding regex.

","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":655,"value":"---\n### Exercise 1","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":694,"value":"How would you select the german verses by T. S. Eliot in the Wasteland?","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":643,"value":"viewof customRegex = Inputs.textarea({\n label: \"Regex\",\n placeholder: \"Write your search pattern\",\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":657,"value":"{\n const highlite = testText.replace(regex3, function (a, b) {\n return \"\" + a + \"\";\n }).replaceAll(\" \", \" \").replaceAll(\"\\n\",\"
\"); \n return html`

${highlite}

`;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":868,"value":"open it in in [☞ regex 101](https://regex101.com/r/YD9qSG/1)","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":863,"value":"---\n### Exercise 2","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":915,"value":"Starting from an unstructured text file containing latitude, longitudes, altitudes and timestamps, how to clean it by selecting only the latitude and longitude?","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":894,"value":"coordinates = FileAttachment(\"ost@2.txt\").text()","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":926,"value":"","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":866,"value":"---\n### Exercise 3","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":951,"value":"Starting from a csv file containing information about wifis, how to obtain a list of custom names? e.g. removing all Vodafone, FRITZ!Box, etc?","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":938,"value":"wifis = FileAttachment(\"out 2.csv\").csv()","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":945,"value":"","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":383,"value":"---\n### Methods","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":22,"value":"text1 = \"The quick brown Fox jumps over the lazy dog.\";","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":69,"value":"$34","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":38,"value":"regex1 = new RegExp(`${regexTable1.regex}`, 'gm');","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":40,"value":"matches1 = text1.match(regex1)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":411,"value":"text2 = `Sent On: Thu, 07 Dec 2006 16:02:59 \n\nJames,\nHereby the site plan \nand image's\n\nJohannes Schwartz\nE: schwartz@hetnieuweinstituut.nl\n\nHet Nieuwe Instituut\nMuseum Park 25\n3015CB Rotterdam\n\n+31 10-4401200\ninfo@hetnieuweinstituut.nl\ncolophon & disclaimer\n\nOPENING HOURS\nTue - Wed 10am - 5pm\nThu 10am - 9pm\nFri - Sun 10am - 5pm\n\nhttps://hetnieuweinstituut.nl/en\n Archive \n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":418,"value":"regexExamples2 = [\n {\n regex: \"\\\\d{2}\\\\s[a-zA-Z]{3}\\\\s\\\\d{4}\",\n description: \"Select a date\"\n },\n {\n regex: \"\\\\+.*?\\\\d{7}\",\n description: \"Select everything in between a + and 7 digits\"\n },\n {\n regex: \"(http|https)://[a-zA-Z0-9-.]+.[a-zA-Z]{2,3}(/S*)?\",\n description: \"Get urls\"\n },\n {\n regex: \"([a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,6})\",\n description: \"Find an email address\"\n },\n {\n regex: \" *.*\",\n description: \"Select html links\"\n }\n]","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":425,"value":"matches2 = text2.match(regex2)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":421,"value":"regex2 = new RegExp(`${regexTable2.regex}`, 'g');","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":668,"value":"$35","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":646,"value":"regex3 = {\n if (customRegex) {\n return new RegExp(`${customRegex}`, \"igms\");\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":720,"value":"testText.match(regex3)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":388,"value":"","pinned":true,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":711,"value":"also, https://regex101.com/r/XXoEaG/1","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"}],"files":"$W36","stdlib":"1","titling":"auto"}} 32:"$31:body"