def retrieve(self, url, filename=None, reporthook=None, data=None):
        url = unwrap(toBytes(url))
        if self.tempcache and url in self.tempcache:
            return self.tempcache[url]
        type, url1 = splittype(url)
        if filename is None and (not type or type == 'file'):
            try:
                fp = self.open_local_file(url1)
                hdrs = fp.info()
                fp.close()
                return url2pathname(splithost(url1)[1]), hdrs
            except IOError:
                pass
        fp = self.open(url, data)
        try:
            headers = fp.info()
            if filename:
                tfp = open(filename, 'wb')
            else:
                import tempfile
                garbage, path = splittype(url)
                garbage, path = splithost(path or "")
                path, garbage = splitquery(path or "")
                path, garbage = splitattr(path or "")
                suffix = os.path.splitext(path)[1]
                (fd, filename) = tempfile.mkstemp(suffix)
                self.__tempfiles.append(filename)
                tfp = os.fdopen(fd, 'wb')
            try:
                result = filename, headers
                if self.tempcache is not None:
                    self.tempcache[url] = result
                bs = 1024*8
                size = -1
                read = 0
                blocknum = 0
                if "content-length" in headers:
                    size = int(headers["Content-Length"])
                if reporthook:
                    reporthook(blocknum, bs, size)
                while 1:
                    block = fp.read(bs)
                    if block == "":
                        break
                    read += len(block)
                    tfp.write(block)
                    blocknum += 1
                    if reporthook:
                        reporthook(blocknum, bs, size)
            finally:
                tfp.close()
        finally:
            fp.close()

        # raise exception if actual size does not match content-length header
        if size >= 0 and read < size:
            raise ContentTooShortError("retrieval incomplete: got only %i out "
                                       "of %i bytes" % (read, size), result)

        return result

    # Each method named open_<type> knows how to open that type of URL
retrieve(url) returns (filename, headers) for a local object
dataset/ETHPy150Open kleientertainment/ds_mod_tools/pkg/win32/Python27/Lib/urllib.py/URLopener.retrieve