Gracefully catch python Exception in Iterator next

Question

I am using PyGithub to scrape some repositories, though I get some error while iterating through the search pages.

def scrape_interval(self, interval):
    for repo_number, repo in self.search(interval):
        code...

def search(self, interval):
    try:
        iterator = enumerate(self.github.search_repositories(query="Laravel created:" + interval))
    except:
        print.warning("Going to sleep for 1 hour. The search API hit the limit")
        time.sleep(3600)
        iterator = self.search(interval)
    return iterator

As you can see I try to catch errors when creating the iterator in def search. But the error is thrown on line for repo_number, repo in self.search(interval): so that is at some point when the iterator get next item?

What are my options to make these errors catchable? I would preferably avoid wrapping the whole for loop in a try clause, rather manage it during the iteration itself.

For reference about the error in itself:

File "/Users/olofjondelius/Documents/Code/laravel-ai/src/examples/migration-analysis/../../GithubScraper.py", line 47, in scrape_interval
    for repo_number, repo in self.search(interval):
  File "/anaconda3/envs/laravel-ai/lib/python3.7/site-packages/github/PaginatedList.py", line 58, in _iter_
    newElements = self._grow()
  File "/anaconda3/envs/laravel-ai/lib/python3.7/site-packages/github/PaginatedList.py", line 70, in _grow
    newElements = self._fetchNextPage()
  File "/anaconda3/envs/laravel-ai/lib/python3.7/site-packages/github/PaginatedList.py", line 172, in _fetchNextPage
    headers=self.__headers
  File "/anaconda3/envs/laravel-ai/lib/python3.7/site-packages/github/Requester.py", line 185, in requestJsonAndCheck
    return self.__check(*self.requestJson(verb, url, parameters, headers, input, cnx))
  File "/anaconda3/envs/laravel-ai/lib/python3.7/site-packages/github/Requester.py", line 231, in requestJson
    return self.__requestEncode(cnx, verb, url, parameters, headers, input, encode)
  File "/anaconda3/envs/laravel-ai/lib/python3.7/site-packages/github/Requester.py", line 284, in __requestEncode
    status, responseHeaders, output = self.__requestRaw(cnx, verb, url, requestHeaders, encoded_input)
  File "/anaconda3/envs/laravel-ai/lib/python3.7/site-packages/github/Requester.py", line 309, in __requestRaw
    requestHeaders
  File "/anaconda3/envs/laravel-ai/lib/python3.7/http/client.py", line 1229, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/anaconda3/envs/laravel-ai/lib/python3.7/http/client.py", line 1275, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/anaconda3/envs/laravel-ai/lib/python3.7/http/client.py", line 1224, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/anaconda3/envs/laravel-ai/lib/python3.7/http/client.py", line 1016, in _send_output
    self.send(msg)
  File "/anaconda3/envs/laravel-ai/lib/python3.7/http/client.py", line 956, in send
    self.connect()
  File "/anaconda3/envs/laravel-ai/lib/python3.7/http/client.py", line 1384, in connect
    super().connect()
  File "/anaconda3/envs/laravel-ai/lib/python3.7/http/client.py", line 928, in connect
    (self.host,self.port), self.timeout, self.source_address)
  File "/anaconda3/envs/laravel-ai/lib/python3.7/socket.py", line 707, in create_connection
    for res in getaddrinfo(host, port, 0, SOCK_STREAM):
  File "/anaconda3/envs/laravel-ai/lib/python3.7/socket.py", line 748, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno 8] nodename nor servname provided, or not known

A suggestion about formatting the exception traceback: Please use code formatting, rather than quote formatting, even if that ends up with long lines. Quote formatting reflows the lines of text, mixing the call locations and code all together into a big mess. And unlike some formatting problems, it is not easy to fix. Somebody who knows what Python tracebacks are supposed to look like can reformat it manually (putting line breaks in at the right places, and indenting each line as best they can), but it's a huge hassle, especially for a traceback like yours that is more than a dozen calls deep. — Blckknght, Jan 09 '19 at 00:16

score 5 · Accepted Answer · answered Jan 09 '19 at 00:08

It sounds like the exception is being raised when you are iterating over the iterator, rather than when you create it. Your current try and except blocks only catch exceptions that are raised immediately when you call self.github.search_repositories, not anything that comes up while you're consuming the results.

To work around that, you could make your search function a generator. That would let you yield values for as long as you have them, but still catch exceptions and retry as often as necessary.

Try something like this:

def search(self, interval):
    while True:
        try:
            it = enumerate(self.github.search_repositories(query="Laravel created:" + interval))
            yield from it
            return   # if we completed the yield from without an exception, we're done!

        except:  # you should probably limit this to catching a specific exception types
            print.warning("Going to sleep for 1 hour. The search API hit the limit")
            time.sleep(3600)

As I noted in a comment, you should probably change the bare except statement to except socket.gaierror or something similar, so that you don't suppress all exceptions but rather only the ones you are expecting and that a delay will fix for you. Something genuinely unexpected should still be allowed to stop the program (since it may reflect a bug elsewhere in your code).

Gracefully catch python Exception in Iterator next

1 Answers1