I would like to convert the following string into an array/nested array:
str = "[[this, is],[a, nested],[array]]"
newarray = # this is what I need help with!
newarray.inspect # => [['this','is'],['a','nested'],['array']]
You'll get what you want with YAML.
But there is a little problem with your string. YAML expects that there's a space behind the comma. So we need this
str = "[[this, is], [a, nested], [array]]"
Code:
require 'yaml'
str = "[[this, is],[a, nested],[array]]"
### transform your string in a valid YAML-String
str.gsub!(/(\,)(\S)/, "\\1 \\2")
YAML::load(str)
# => [["this", "is"], ["a", "nested"], ["array"]]
You could also treat it as almost-JSON. If the strings really are only letters, like in your example, then this will work:
JSON.parse(yourarray.gsub(/([a-z]+)/,'"\1"'))
If they could have arbitrary characters (other than [ ] , ), you'd need a little more:
JSON.parse("[[this, is],[a, nested],[array]]".gsub(/, /,",").gsub(/([^\[\]\,]+)/,'"\1"'))
For a laugh:
ary = eval("[[this, is],[a, nested],[array]]".gsub(/(\w+?)/, "'\\1'") )
=> [["this", "is"], ["a", "nested"], ["array"]]
Disclaimer: You definitely shouldn't do this as eval is a terrible idea, but it is fast and has the useful side effect of throwing an exception if your nested arrays aren't valid
Looks like a basic parsing task. Generally the approach you are going to want to take is to create a recursive function with the following general algorithm
base case (input doesn't begin with '[') return the input
recursive case:
split the input on ',' (you will need to find commas only at this level)
for each sub string call this method again with the sub string
return array containing the results from this recursive method
The only slighlty tricky part here is splitting the input on a single ','. You could write a separate function for this that would scan through the string and keep a count of the openbrackets - closedbrakets seen so far. Then only split on commas when the count is equal to zero.
Make a recursive function that takes the string and an integer offset, and "reads" out an array. That is, have it return an array or string (that it has read) and an integer offset pointing after the array. For example:
s = "[[this, is],[a, nested],[array]]"
yourFunc(s, 1) # returns ['this', 'is'] and 11.
yourFunc(s, 2) # returns 'this' and 6.
Then you can call it with another function that provides an offset of 0, and makes sure that the finishing offset is the length of the string.
Related
I have a string "990822". I want to know if the string starts with "99".
I could achieve this by getting the first two characters of the string, then check if this is equal to "99". How do I get the first two characters from a string?
You can use String#start_with?:
"990822".start_with?("99") #=> true
Consider using the method start_with?.
s = "990822"
=> "990822"
s.start_with? "99"
=> true
You can use a range to access string:
"990822"[0...2]
# => "99"
See the String docs
To get the first two characters, the most straightforward way is:
"990822"[0, 2] # => "99"
Using a range inside the method [] is both not straightforward and also creates a range object that is immediately thrown out, which is a waste.
However, the whole question is actually an XY-question.
I have an array that is in string form
"[{"img_type":"HA","img_size":0,"img_name":"8a040ff1-e780-4843-9f01-6dc37e11f3c8"},{"img_type":"HB","img_size":0,"img_name":"8a040ff1-e780-4843-9f01-6dc37e11f3c8"}]"
I need to convert that to
[
{"img_type": "HA", "img_size": 0, "img_name": "8a040ff1-e780-4843-9f01-6dc37e11f3c8"},
{"img_type": "HB", "img_size": 0, "img_name": "8a040ff1-e780-4843-9f01-6dc37e11f3c8"}
]
I tried removing double quotes, but it didn't work. How can I convert this to an array?
str = '[{"img_type":"HA","img_size":0,"img_name":"8a040ff1-e780-4843-9f01-6dc37e11f3c8"},{"img_type":"HB","img_size":0,"img_name":"8a040ff1-e780-4843-9f01-6dc37e11f3c8"}]'
require 'json'
JSON.parse(str, symbolize_names: true)
#=> [{:img_type=>"HA", :img_size=>0, :img_name=>"8a040ff1-e780-4843-9f01-6dc37e11f3c8"},
# {:img_type=>"HB", :img_size=>0, :img_name=>"8a040ff1-e780-4843-9f01-6dc37e11f3c8"}]
Notice that JSON::parse provides for several optional parameters, one of which (symbolize_names) "returns symbols for the names (keys) in a JSON object. Otherwise strings are returned."
Try this,
str = '[{"img_type":"HA","img_size":0,"img_name":"8a040ff1-e780-4843-9f01-6dc37e11f3c8"},{"img_type":"HB","img_size":0,"img_name":"8a040ff1-e780-4843-9f01-6dc37e11f3c8"}]'
array = eval(str)
This may solve your purpose but its nasty to use eval as it brings serious danger of undefined methods and SQL injection.
Prefer JSON.parse(your_string)for this purpose.
I've had a look round and can't find what I need on Stack Overflow, and was wondering if someone had a simple solution.
I want to find a parameter within a URL and increment its value, so, as an example:
?kws=&pstc=&cty=&prvnm=1
I want to be able to locate the prvnm parameter no matter where it is in the string and increment its value by 1.
I know I could split the parameters into an array, find the key, increment it and write it back but that seems rather long winded and wondered if someone else had any ideas!
require "uri"
url = "http://example.com/?kws=&pstc=&cty=&prvnm=1"
def new_url(url)
uri = URI.parse(url)
hsh = Hash[URI.decode_www_form(uri.query)]
hsh['prvnm'] = hsh['prvnm'].next
uri.query = URI.encode_www_form(hsh).to_s
uri.to_s
end
new_url(url) # => "http://example.com/?kws=&pstc=&cty=&prvnm=2"
There are already four answers, so I had to come up with something a little different:
s = "?kws=&pstc=&cty=&prvnm=1"
head, sep, tail = s.partition(/(?<=[?&]prvnm=)\d+/)
head + (sep.to_i + 1).to_s + tail # => "?kws=&pstc=&cty=&prvnm=2"
'String#partition' returns an array of three strings [head, sep, tail], such that head + sep + tail => s, where separator is partition's argument, which can be a string or a regex.
We want the separator to be the digits following &prvnm=. We therefore use a regex with \d+ preceeded by the aforementioned string which we want to treat as having zero length, so it will not be included in the separator. That calls for a "positive look-behind": (?<=&prvnm=). \d+ is "greedy", so it take all consequetive digits.
For the given value of s, head, sep, tail = s.partition(/(?<=&prvnm=)(\d+)/)
=> ["?kws=&pstc=&cty=&prvnm=", "1", ""].
Edit: my thanks to #quetzalcoatl for pointing out that I needed to change (?<=&prvnm=) in my regex to what I have now, as what I had would fail when ?prvnm= was at the beginning of the string.
split the string by `&`
then iterate over the parts
then split each part by `=` and inspect the results
when found `prvnm`, parse the integer and increment it
then join the bits by '='
then join the parts by '&'
Or, use regex like:
/[?&]prvnm=\d+/
and parse the result and then do a replacement.
Or, get some URL-parsing library..
Try something like this:
params = "?kws=&pstc=&cty=&prvnm=1"
num = params.scan(/prvnm=(\d)/)[0].join.to_i
puts num + 1
Use:
require 'uri'
Then:
parsed-url= URI.parse( ur full url)
r = CGI.parse(parsed_url.query)
r is now a hash of all your query parameters.
You can easily access it by using:
r["prsvn"].to_i + 1
In Ruby, what regex will strip out all but a desired string if present in the containing string? I know about /[^abc]/ for characters, but what about strings?
Say I have the string "group=4&type_ids[]=2&type_ids[]=7&saved=1" and want to retain the pattern group=\d, if it is present in the string using only a regex?
Currently, I am splitting on & and then doing a select with matching condition =~ /group=\d/ on the resulting enumerable collection. It works fine, but I'd like to know the regex to do this more directly.
Simply:
part = str[/group=\d+/]
If you want only the numbers, then:
group_str = str[/group=(\d+)/,1]
If you want only the numbers as an integer, then:
group_num = str[/group=(\d+)/,1].to_i
Warning: String#[] will return nil if no match occurs, and blindly calling nil.to_i always returns 0.
You can try:
$str =~ s/.*(group=\d+).*/\1/;
Typically I wouldn't really worry too much about a complex regex. Simply break the string down into smaller parts and it becomes easier:
asdf = "group=4&type_ids[]=2&type_ids[]=7&saved=1"
asdf.split('&').select{ |q| q['group'] } # => ["group=4"]
Otherwise, you can use regex a bunch of different ways. Here's two ways I tend to use:
asdf.scan(/group=\d+/) # => ["group=4"]
asdf[/(group=\d+)/, 1] # => "group=4"
Try:
str.match(/group=\d+/)[0]
I have a text file from which I want to create a Hash for faster access. My text file is of format (space delimited)
author title date popularity
I want to create a hash in which author is the key and the remaining is the value as an array.
created_hash["briggs"] = ["Manup", "Jun,2007", 10]
Thanks in advance.
require 'date'
created_hash = File.foreach('test.txt', mode: 'rt', encoding: 'UTF-8').
reduce({}) {|hsh, l|
name, title, date, pop = l.split
hsh.tap {|hsh| hsh[name] = [title, Date.parse(date), pop.to_i] }
}
I threw some type conversion code in there, just for fun. If you don't want that, the loop body becomes even simpler:
k, *v = l.split
hsh.tap {|hsh| hsh[k] = v }
You can also use readlines instead of foreach. Note that IO#readlines reads the entire file into an array first. So, you need enough memory to hold both the entire array and the entire hash. (Of course, the array will be eligible for garbage collection as soon as the loop finishes.)
Just loop through each line of the file, use the first space-delimited item as the hash key and the rest as the hash value. Pretty much exactly as you described.
created_hash = {}
file_contents.each_line do |line|
data = line.split(' ')
created_hash[data[0]] = data.drop 1
end