How can I extract a substring from within a string in Ruby?
Example:
String1 = "<name> <substring>"
I want to extract substring from String1 (i.e. everything within the last occurrence of < and >).
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5 Answers
"<name> <substring>"[/.*<([^>]*)/,1]
=> "substring"
No need to use scan, if we need only one result.
No need to use Python's match, when we have Ruby's String[regexp,#].
See: http://ruby-doc.org/core/String.html#method-i-5B-5D
Note: str[regexp, capture] → new_str or nil
9 Comments
coreyward
No need to discredit other perfectly valid (and might I opine, more readable) solutions.
Nakilon
@coreyward, if they are better, please, argument it. For example, sepp2k's solution is more flexible, and that's why I pointed
if we need only one result in my solution. And match()[] is slower, because it's two methods instead of one.
Wayne Conrad
This is the fastest of all the methods presented, but even the slowest method takes only 4.5 microseconds on my machine. I do not care to speculate why this method is faster. In performance, speculation is useless. Only measurement counts.
Ryan H.
I find this solution more straightforward and to the point (since I am new to Ruby). Thanks.
Nick
@Nakilon Readability can outweigh tiny performance differences when considering the overall success of a product and team, so coreyward made a valid comment. That said, I think
string[regex] can be just as readable in this scenario, so that's what I used personally. |
String1.scan(/<([^>]*)>/).last.first
scan creates an array which, for each <item> in String1 contains the text between the < and the > in a one-element array (because when used with a regex containing capturing groups, scan creates an array containing the captures for each match). last gives you the last of those arrays and first then gives you the string in it.
Comments
You can use a regular expression for that pretty easily…
Allowing spaces around the word (but not keeping them):
str.match(/< ?([^>]+) ?>\Z/)[1]
Or without the spaces allowed:
str.match(/<([^>]+)>\Z/)[1]
Here's a slightly more flexible approach using the match method. With this, you can extract more than one string:
s = "<ants> <pants>"
matchdata = s.match(/<([^>]*)> <([^>]*)>/)
# Use 'captures' to get an array of the captures
matchdata.captures # ["ants","pants"]
# Or use raw indices
matchdata[0] # whole regex match: "<ants> <pants>"
matchdata[1] # first capture: "ants"
matchdata[2] # second capture: "pants"
answered Aug 30, 2013 at 19:04
Grant Birchmeier
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Comments
A simpler scan would be:
String1.scan(/<(\S+)>/).last
