Convert python search regex to ruby regex

Question

I'm trying to convert the following python regex to ruby

match = re.search(r'window.__APOLLO_STATE__ = JSON.parse\("(.+?)"\);', body)

I've done some digging and Regexp#match should be what i'm looking for but the following is returning nil.

resp.body.match('^window.__APOLLO_STATE__ = JSON.parse\("(.+?)"\)')

How can I convert the regex and where am I wrong?

You probably want to pass a Regexp object to `match` rather than a string, i.e. `/^window.__APOLLO_.../`. — Jordan Running, Dec 04 '19 at 23:04
Use `resp.body[/window\.__APOLLO_STATE__ = JSON\.parse$"(.*?)"$;/, 1]`, see https://ideone.com/sJth9I — Wiktor Stribiżew, Dec 04 '19 at 23:16

score 1 · Accepted Answer · answered Dec 05 '19 at 00:38

You may use

resp.body[/window\.__APOLLO_STATE__ = JSON\.parse\("(.*?)"\);/, 1]

Here,

/.../ is a regex literal notation that is very convenient when defining regex patterns
Literal dots are escaped, else, they match any char but line break chars
The .+? is changed to .*? to be able to match empty values (else, you may overmatch, it is easier to later discard empty matches than fix overmatches)
1 tells the engine to return the value of the capturing group with ID 2 of the first match. If you need multiple matches, use resp.body.scan(/regex/).

score 0 · Answer 2 · answered Dec 04 '19 at 23:31

An idiomatic way is to use the =~ regex match operator:

resp.body =~ /^window.__APOLLO_STATE__ = JSON.parse\("(.+?)"\)/

You can access the capture groups with $1, $2, and so on.

If you don't like the global variable usage, you can also use the Regexp#match method

result = /^window.__APOLLO_STATE__ = JSON.parse\("(.+?)"\)/.match(resp.body)
result[1] # => returns first capture group

Cary Swoveland · Answer 3 · 2019-12-05T03:24:36.740

As I understand, your string is something like

str = 'window.__APOLLO_STATE__ = JSON.parse("my dog has fleas");'

and you wish to extract the text between the double quotes. You can do that with the following regular expression, which does not employ a capture group:

r = /\Awindow\.__APOLLO_STATE__ = JSON\.parse\(\"\K.+?(?=\"\);\z)/

str[r]
  #=> "my dog has fleas"

The regular expression can be written in free-spacing mode to make it self-documenting:

r = /
    \A          # match beginning of string
    window\.__APOLLO_STATE__\ =\ JSON\.parse\(\"
                # match substring
    \K          # discard everything matched so far 
    .+?         # match 1+ characters, lazily
    (?=\"\);\z) # match "); followed by end-of-string (positive lookahead)
    /x          # free-spacing regex definition mode

The contents of a positive lookahead must be matched but are not part of the match returned. Neither is the text matched prior to the \K directive part of the match returned.

Free-spacing mode removes all whitespace before the expression is parsed. Accordingly, any intended spaces (in "APOLLO_STATE__ = JSON", for example) must be protected. I've done that by escaping the spaces, one of several ways that can be done.

Convert python search regex to ruby regex

3 Answers3