Metadata-Version: 2.1
Name: chompjs
Version: 1.1.8
Summary: Parsing JavaScript objects into Python dictionaries
Home-page: https://github.com/Nykakin/chompjs
Author: Mariusz Obajtek
Author-email: nykakin@gmail.com
License: UNKNOWN
Description: # Usage
        
        `chompjs` can be used in web scrapping for turning JavaScript objects embedded in pages into valid Python dictionaries.
        
        ```python
        >>> import chompjs
        >>> chompjs.parse_js_object('{"my_data": "test"}')
        {u'my_data': u'test'}
        ```
        
        Think of it as a more powerful `json.loads`. For example, it can handle JSON objects containing embedded methods by storing their code in a string:
        
        ```python
        >>> import chompjs
        >>> js = """
        ... var myObj = {
        ...     myMethod: function(params) {
        ...         // ...
        ...     },
        ...     myValue: 100
        ... }
        ... """
        >>> chompjs.parse_js_object(js, json_params={'strict': False})
        {'myMethod': 'function(params) {\n        // ...\n    }', 'myValue': 100}
        ```
        
        An example usage with `scrapy`:
        
        ```python
        import chompjs
        import scrapy
        
        
        class MySpider(scrapy.Spider):
            # ...
        
            def parse(self, response):
                script_css = 'script:contains("__NEXT_DATA__")::text'
                script_pattern = r'__NEXT_DATA__ = (.*);'
                # warning: for some pages you need to pass replace_entities=True
                # into re_first to have JSON escaped properly
                script_text = response.css(script_css).re_first(script_pattern)
                try:
                    json_data = chompjs.parse_js_object(script_text)
                except ValueError:
                    self.log('Failed to extract data from {}'.format(response.url))
                    return
        
                # work on json_data
        ```
        
        If the input string is not yet escaped and contains a lot of `\\` characters, then `unicode_escape=True` argument might help to sanitize it:
        
        ```python
        >>> chompjs.parse_js_object('{\\\"a\\\": 12}', unicode_escape=True)
        {u'a': 12}
        ```
        
        `jsonlines=True` can be used to parse JSON Lines:
        
        ```python
        >>> chompjs.parse_js_object('[1,2]\n[2,3]\n[3,4]', jsonlines=True)
        [[1, 2], [2, 3], [3, 4]]
        ```
        
        By default `chompjs` tries to start with first `{` or `[` character it founds, omitting the rest:
        
        ```python
        >>> chompjs.parse_js_object('<div>...</div><script>foo = [1, 2, 3];</script><div>...</div>')
        [1, 2, 3]
        ```
        
        `json_params` argument can be used to pass options to underlying `json_loads`, such as `strict` or `object_hook`:
        
        ```python
        >>> import decimal
        >>> import chompjs
        >>> chompjs.parse_js_object('[23.2]', json_params={'parse_float': decimal.Decimal})
        [Decimal('23.2')]
        ```
        
        # Rationale
        
        In web scraping data often is not present directly inside HTML, but instead provided as an embedded JavaScript object that is later used to initialize the page, for example:
        
        ```html
        <html>
        <head>...</head>
        <body>
        ...
        <script type="text/javascript">window.__PRELOADED_STATE__={"foo": "bar"}</script>
        ...
        </body>
        </html>
        ```
        
        Standard library function `json.loads` is usually sufficient to extract this data:
        
        ```python
        >>> # scrapy shell file:///tmp/test.html
        >>> import json
        >>> script_text = response.css('script:contains(__PRELOADED_STATE__)::text').re_first('__PRELOADED_STATE__=(.*)')
        >>> json.loads(script_text)
        {u'foo': u'bar'}
        
        ```
        The problem is that not all valid JavaScript objects are also valid JSONs. For example all those strings are valid JavaScript objects but not valid JSONs:
        
        * `"{'a': 'b'}"` is not a valid JSON because it uses `'` character to quote
        * `'{a: "b"}'`is not a valid JSON because property name is not quoted at all
        * `'{"a": [1, 2, 3,]}'` is not a valid JSON because there is an extra `,` character at the end of the array
        * `'{"a": .99}'` is not a valid JSON because float value lacks a leading 0
        
        As a result, `json.loads` fail to extract any of those:
        
        ```
        >>> json.loads("{'a': 'b'}")
        Traceback (most recent call last):
          File "<console>", line 1, in <module>
          File "/usr/lib/python2.7/json/__init__.py", line 339, in loads
            return _default_decoder.decode(s)
          File "/usr/lib/python2.7/json/decoder.py", line 364, in decode
            obj, end = self.raw_decode(s, idx=_w(s, 0).end())
          File "/usr/lib/python2.7/json/decoder.py", line 380, in raw_decode
            obj, end = self.scan_once(s, idx)
        ValueError: Expecting property name: line 1 column 2 (char 1)
        >>> json.loads('{a: "b"}')
        Traceback (most recent call last):
          File "<console>", line 1, in <module>
          File "/usr/lib/python2.7/json/__init__.py", line 339, in loads
            return _default_decoder.decode(s)
          File "/usr/lib/python2.7/json/decoder.py", line 364, in decode
            obj, end = self.raw_decode(s, idx=_w(s, 0).end())
          File "/usr/lib/python2.7/json/decoder.py", line 380, in raw_decode
            obj, end = self.scan_once(s, idx)
        ValueError: Expecting property name: line 1 column 2 (char 1)
        >>> json.loads('{"a": [1, 2, 3,]}')
        Traceback (most recent call last):
          File "<console>", line 1, in <module>
          File "/usr/lib/python2.7/json/__init__.py", line 339, in loads
            return _default_decoder.decode(s)
          File "/usr/lib/python2.7/json/decoder.py", line 364, in decode
            obj, end = self.raw_decode(s, idx=_w(s, 0).end())
          File "/usr/lib/python2.7/json/decoder.py", line 382, in raw_decode
            raise ValueError("No JSON object could be decoded")
        ValueError: No JSON object could be decoded
        >>> json.loads('{"a": .99}')
        Traceback (most recent call last):
          File "<stdin>", line 1, in <module>
          File "/usr/lib/python3.7/json/__init__.py", line 348, in loads
            return _default_decoder.decode(s)
          File "/usr/lib/python3.7/json/decoder.py", line 337, in decode
            obj, end = self.raw_decode(s, idx=_w(s, 0).end())
          File "/usr/lib/python3.7/json/decoder.py", line 355, in raw_decode
            raise JSONDecodeError("Expecting value", s, err.value) from None
        json.decoder.JSONDecodeError: Expecting value: line 1 column 7 (char 6)
        
        ```
        `chompjs` library was designed to bypass this limitation, and it allows to scrape such JavaScript objects into proper Python dictionaries:
        
        ```
        >>> import chompjs
        >>> 
        >>> chompjs.parse_js_object("{'a': 'b'}")
        {u'a': u'b'}
        >>> chompjs.parse_js_object('{a: "b"}')
        {u'a': u'b'}
        >>> chompjs.parse_js_object('{"a": [1, 2, 3,]}')
        {u'a': [1, 2, 3]}
        ```
        
        Internally `chompjs` use a parser written in C to iterate over raw string, fixing its issues along the way. The final result is then passed down to standard library's `json.loads`, ensuring a high speed as compared to full-blown JavaScript parsers such as `demjson`.
        
        ```
        >>> import json
        >>> import _chompjs
        >>> 
        >>> _chompjs.parse('{a: 1}')
        '{"a":1}'
        >>> json.loads(_)
        {u'a': 1}
        >>> chompjs.parse_js_object('{"a": .99}')
        {'a': 0.99}
        ```
        
        # Installation
        From PIP:
        
        ```bash
        $ python3 -m venv venv
        $ . venv/bin/activate
        # pip install chompjs
        ```
        From sources:
        ```bash
        $ git clone https://github.com/Nykakin/chompjs
        $ cd chompjs
        $ python setup.py build
        $ python setup.py install
        ```
        
        To run unittests
        
        ```
        $ python -m unittest
        ```
        
Keywords: parsing parser JavaScript json
Platform: UNKNOWN
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: JavaScript
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Classifier: Topic :: Text Processing :: General
Classifier: Topic :: Text Processing :: Linguistic
Description-Content-Type: text/markdown
