I have these 2 things I am working with:
CSV.foreach('datafile.csv','r') {|row| D_Location << row[0]}
puts Date.new(2003,05,02).cwday
In the first line I would like to change the datafile.csv to something like a string so I can change one string and it changes for all of these codes. I have many, each controlling 1 csv column.
In the second one I would like to replace the actual date written, and replace it with a string. This is so that can be automatic, because the string will be generated based on other criteria.
I trust the mods will ban me if I'm being too much of a noob hehe. Then I'll toughen up and find these answers myself eventually. But so far I've solved a lot, but not this. Thanks in advance!
Make a function which takes in a string representing a weekday, and returns a number. Call this function later in your code:
Date.new(2003, 05, yourfun('Tuesday')).cwday
For the first part of your question, you're already working with a string. I think what you mean is that you want it to be in a variable:
csv_file = 'datafile.csv'
CSV.foreach(csv_file,'r') {|row| D_Location << row[0]}
For the second part of your question, Date.parse() works with strings, but they need to be in a format that it can recognize. If your date strings use commas, you can replace them with hyphens:
date_str = "2003,05,02"
Date.parse(date_str.gsub(",", "-")).cwday # => 5
It's not clear where your date strings will be coming from or what format they'll be in, but the general concepts you need to understand are that you can use variables, and that you can transform strings.
Related
I'm new here, so please don't scold me for misspellings etc.
What I need to do is to rename a bunch of files with a date in different formats at the beginning of their names, like:
05.07.2020-abc.pdf
2020.07.05-pqr.pdf
Instead of writing a different expression for each formatting, eg.
^(\d{2})\.(\d{2}).(\d{4})(.+) => $3-$2-$1$4
Example
02.11.2022-abc.pdf => 2022-11-02-abc.pdf
I'd like to do it in one fell swoop using the OR operator "|" but I have no idea how to formulate the groupings etc. Can one have nested groupings in regex?
Any ideas? Thank in advance!
#The fourth bird:
No (.+) needed. You're right, I condensed my actual expression and could have taken it out.
The different date 'formats' I mean are dd.mm.yyyy and yyyy.mm.dd respectively, and I need to convert both to yyyy-mn-dd
So,if the format is dd.mm.yyyy I have to flip the string, so to say, else I just need to replace the dots by hyphens.
The OS is Android, and for this operation I use Solid Explorer multi search & replace using regex.
I hope I made myself clear this time around ;-)
I would like to extract a line of strings but am having difficulties using the correct RegEx. Any help would be appreciated.
String to extract: KSEA 122053Z 21008KT 10SM FEW020 SCT250 17/08 A3044 RMK AO2 SLP313 T01720083 50005
For Some reason StackOverflow wont let me cut and paste the XML data here since it includes "<>" characters. Basically I am trying to extract data between "raw_text" ... "/raw_text" from a xml that will always be formatted like the following: http://www.aviationweather.gov/adds/dataserver_current/httpparam?dataSource=metars&requestType=retrieve&format=xml&hoursBeforeNow=3&mostRecent=true&stationString=PHNL%20KSEA
However, the Station name, in this case "KSEA" will not always be the same. It will change based on user input into a search variable.
Thanks In advance
if I can assume that every strings that you want starts with KSEA, then the answer would be:
.*(KSEA.*?)KSEA.*
using ? would let .* match as less as possible.
I have a string which is a function call. I want to parse it and obtain the parameters:
"add_location('http://abc.com/page/1/','This is the title, it is long',39.677765,-45.4343,34454,'http://abc.com/images/image_1.jpg')"
It has a total of 6 parameters and is a mixture of urls, integers and decimals. I can't figure out the regex for the split method which I will be using. Please help!
This is what I have come up with - which is wrong.
/('(.*\/[0-9]*)',)|([0-9]*,)/
Treating the string like a CSV might work:
require 'csv'
str = "add_location('http://abc.com/page/1/','This is the title, it is long',39.677765,-45.4343,34454,'http://abc.com/images/image_1.jpg')"
p CSV.parse(str[13..-2], :quote_char => "'").first
# => ["http://abc.com/page/1/", "This is the title, it is long", "39.677765", "-45.4343", "34454", "http://abc.com/images/image_1.jpg"]
Assuming all non-numeric parameters are enclosed in single quotes, as in your example
string.scan( /'.+?'|[-0-9.]+/ )
You really don't want to be parsing things this complex with a reg-ex; it just won't work in the long run. I'm not sure if you just want to parse this one string, or if there are lots of strings in this form which vary in exact contents. If you give a bit more info about your end goal, you might be able to get some more detailed help.
For parsing things this complex in the general case, you really want to perform proper tokenization (i.e. lexical analysis) of the string. In the past with Ruby, I've had good experiences doing this with Citrus. It's a nice gem for parsing complex tokens/languages like you're trying to do. You can find more about it here:
https://github.com/mjijackson/citrus
I am learning Ruby, and in the book I use, there is an example code like this
#...
restaurant = Restaurant.new
restaurant.name = "Mediterrano"
restaurant.description = <<DESC
One of the best Italian restaurants in the Kings Cross area,
Mediterraneo will never leave you disappointed
DESC
#...
Can someone explain to me what <<DESC means in the above example? How does it differ from the common string double quote?
It is used to create multiline strings. Basically, '<< DESC' tells ruby to consider everything that follows until the next 'DESC' keyword. 'DESC' is not mandatory, as it can be replaced with anything else.
a = <<STRING
Here
is
a
multiline
string
STRING
The << operator is followed by an identifier that marks the end of the document. The end mark is called the terminator. The lines of text prior to the terminator are joined together, including the newlines and any other whitespace.
http://en.wikibooks.org/wiki/Ruby_Programming/Here_documents
It allows the creation of multi-line string constants in a readable way. See http://en.wikibooks.org/wiki/Ruby_Programming/Here_documents.
It is called a heredoc, or heredocument. It allows you to write multiline. You can test it in your terminal!
I'm too ambitious or is there a way do this
to add a string if not present ?
and
remove a the same string if present?
Do all of this using Regex and avoid the if else statement
Here an example
I have string
"admin,artist,location_manager,event_manager"
so can the substring location_manager be added or removed with regards to above conditions
basically I'm looking to avoid the if else statement and do all of this plainly in regex
"admin,artist,location_manager,event_manager".test(/some_regex/)
The some_regex will remove location_manager from the string if present else it will add it
Am I over over ambitions
You will need to use some sort of logic.
str += ',location_manager' unless str.gsub!(/location_manager,/,'')
I'm assuming that if it's not present you append it to the end of the string
Regex will not actually add or remove anything in any language that I am aware of. It is simply used to match. You must use some other language construct (a regex based replacement function for example) to achieve this functionality. It would probably help to mention your specific language so as to get help from those users.
Here's one kinda off-the-wall solution. It doesn't use regexes, but it also doesn't use any if/else statements either. It's more academic than production-worthy.
Assumptions: Your string is a comma-separated list of titles, and that these are a unique set (no duplicates), and that order doesn't matter:
titles = Set.new(str.split(','))
#=> #<Set: {"admin", "artist", "location_manager", "event_manager"}>
titles_to_toggle = ["location_manager"]
#=> ["location_manager"]
titles ^= titles_to_toggle
#=> #<Set: {"admin", "artist", "event_manager"}>
titles ^= titles_to_toggle
#=> #<Set: {"location_manager", "admin", "artist", "event_manager"}>
titles.to_a.join(",")
#=> "location_manager,admin,artist,event_manager"
All this assumes that you're using a string as a kind of set. If so, you should probably just use a set. If not, and you actually need string-manipulation functions to operate on it, there's probably no way around except for using if-else, or a variant, such as the ternary operator, or unless, or Bergi's answer
Also worth noting regarding regex as a solution: Make sure you consider the edge cases. If 'location_manager' is in the middle of the string, will you remove the extraneous comma? Will you handle removing commas correctly if it's at the beginning or the end of the string? Will you correctly add commas when it's added? For these reasons treating a set as a set or array instead of a string makes more sense.
No. Regex can only match/test whether "a string" is present (or not). Then, the function you've used can do something based on that result, for example replace can remove a match.
Yet, you want to do two actions (each can be done with regex), remove if present and add if not. You can't execute them sequentially, because they overlap - you need to execute either the one or the other. This is where if-else structures (or ternary operators) come into play, and they are required if there is no library/native function that contains them to do exactly this job. I doubt there is one in Ruby.
If you want to avoid the if-else-statement (for one-liners or expressions), you can use the ternary operator. Or, you can use a labda expression returning the correct value:
# kind of pseudo code
string.replace(/location,?|$/, function($0) return $0 ? "" : ",location" )
This matches the string "location" (with optional comma) or the string end, and replaces that with nothing if a match was found or the string ",location" otherwise. I'm sure you can adapt this to Ruby.
to remove something matching a pattern is really easy:
(admin,?|artist,?|location_manager,?|event_manager,?)
then choose the string to replace the match -in your case an empty string- and pass everything to the replace method.
The other operation you suggested was more difficult to achieve with regex only. Maybe someone knows a better answer