Browsermob selenium python - JSONDecodeError

Question

Trying to get HAR files for a bunch of urls using browsermob-proxy with selenium in Python. For the basic implementation, I'm using the sample code from Browsermob documentation . My code below

from browsermobproxy import Server
import psutil
import time

server = Server(“/path/to/bin/browsermob-proxy")
server.start()
proxy = server.create_proxy()

from selenium import webdriver
profile  = webdriver.FirefoxProfile()
profile.set_proxy(proxy.selenium_proxy())
driver = webdriver.Firefox(firefox_profile=profile)

proxy.new_har(“google”) 
driver.get("http://www.google.com")
print(proxy.har) #ISSUE IN THIS LINE

server.stop()
driver.quit()

I'm able to initialize browsermob-proxy, and get selenium to open the page on firefox (and chrome). When it gets to the 'proxy.har' line, it throws a JSONDecodeError: Expecting value: line 1 column 1 (char 0)

Error trace below

JSONDecodeError                           Traceback (most recent call last)
<ipython-input-2-f690bb4c2c08> in <module>()
----> 1 proxy.har

~/anaconda3/lib/python3.6/site-packages/browsermobproxy/client.py in har(self)
    102         r = requests.get('%s/proxy/%s/har' % (self.host, self.port))
    103 
--> 104         return r.json()
    105 
    106     def new_har(self, ref=None, options=None, title=None):

~/anaconda3/lib/python3.6/site-packages/requests/models.py in json(self, **kwargs)
    890                     # used.
    891                     pass
--> 892         return complexjson.loads(self.text, **kwargs)
    893 
    894     @property

~/anaconda3/lib/python3.6/json/__init__.py in loads(s, encoding, cls, object_hook, parse_float, parse_int, parse_constant, object_pairs_hook, **kw)
    352             parse_int is None and parse_float is None and
    353             parse_constant is None and object_pairs_hook is None and not kw):
--> 354         return _default_decoder.decode(s)
    355     if cls is None:
    356         cls = JSONDecoder

~/anaconda3/lib/python3.6/json/decoder.py in decode(self, s, _w)
    337 
    338         """
--> 339         obj, end = self.raw_decode(s, idx=_w(s, 0).end())
    340         end = _w(s, end).end()
    341         if end != len(s):

~/anaconda3/lib/python3.6/json/decoder.py in raw_decode(self, s, idx)
    355             obj, end = self.scan_once(s, idx)
    356         except StopIteration as err:
--> 357             raise JSONDecodeError("Expecting value", s, err.value) from None
    358         return obj, end

JSONDecodeError: Expecting value: line 1 column 1 (char 0)

I've tried a bunch of things to resolve this, but can't get it to work

• The GET request returns 200
• Tried some json functions to load or parse to utf-8 or strip invalid characters
• Tried simplejson
• Tried changing browsermob port
• Tried on different networks in case the block was being caused by proxy settings

I get the same error no matter what I try. I initially thought the issue was with my installation. This is how I did it:

1. Installed selenium using pip3 (using python 3.6 with Jupyter/iPython)
2. Downloaded browsermob binary from https://bmp.lightbody.net/
3. Downloaded geckodriver
4. Started the proxy using ./browsermob-proxy within /bin, and also tried selecting the port using -port

Anyone had similar issues, which they resolved using anything other than the ones described above?

Answer 1

The problem is that the "browsermob-proxy" package is not compatible with your Python version. The package is written for Python 2.x, while you are using Python 3.6.

Answer 2

I had the very same issue when running Python 3.6 on OSX 10.14.

Solved by switching to Python 3.7 - works on both Linux and Mac.