use context management when processing Tiger data

nominatim/tools/tiger_data.py

@@ -21,33 +21,57 @@ from nominatim.indexer.place_info import PlaceInfo
 
 LOG = logging.getLogger()
 
-
-def handle_tarfile_or_directory(data_dir):
-    """ Handles tarfile or directory for importing tiger data
+class TigerInput:
+    """ Context manager that goes through Tiger input files which may
+        either be in a directory or gzipped together in a tar file.
     """
 
-    tar = None
+    def __init__(self, data_dir):
+        self.tar_handle = None
+        self.files = []
+
         if data_dir.endswith('.tar.gz'):
             try:
-            tar = tarfile.open(data_dir)
+                self.tar_handle = tarfile.open(data_dir) # pylint: disable=consider-using-with
             except tarfile.ReadError as err:
                 LOG.fatal("Cannot open '%s'. Is this a tar file?", data_dir)
                 raise UsageError("Cannot open Tiger data file.") from err
 
-        csv_files = [i for i in tar.getmembers() if i.name.endswith('.csv')]
-        LOG.warning("Found %d CSV files in tarfile with path %s", len(csv_files), data_dir)
-        if not csv_files:
-            LOG.warning("Tiger data import selected but no files in tarfile's path %s", data_dir)
-            return None, None
+            self.files = [i for i in self.tar_handle.getmembers() if i.name.endswith('.csv')]
+            LOG.warning("Found %d CSV files in tarfile with path %s", len(self.files), data_dir)
         else:
             files = os.listdir(data_dir)
-        csv_files = [os.path.join(data_dir, i) for i in files if i.endswith('.csv')]
-        LOG.warning("Found %d CSV files in path %s", len(csv_files), data_dir)
-        if not csv_files:
-            LOG.warning("Tiger data import selected but no files found in path %s", data_dir)
-            return None, None
+            self.files = [os.path.join(data_dir, i) for i in files if i.endswith('.csv')]
+            LOG.warning("Found %d CSV files in path %s", len(self.files), data_dir)
 
-    return csv_files, tar
+        if not self.files:
+            LOG.warning("Tiger data import selected but no files found at %s", data_dir)
+
+
+    def __enter__(self):
+        return self
+
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if self.tar_handle:
+            self.tar_handle.close()
+            self.tar_handle = None
+
+
+    def next_file(self):
+        """ Return a file handle to the next file to be processed.
+            Raises an IndexError if there is no file left.
+        """
+        fname = self.files.pop(0)
+
+        if self.tar_handle is not None:
+            return io.TextIOWrapper(self.tar_handle.extractfile(fname))
+
+        return open(fname, encoding='utf-8')
+
+
+    def __len__(self):
+        return len(self.files)
 
 
 def handle_threaded_sql_statements(pool, fd, analyzer):
@@ -79,9 +103,9 @@ def add_tiger_data(data_dir, config, threads, tokenizer):
     """ Import tiger data from directory or tar file `data dir`.
     """
     dsn = config.get_libpq_dsn()
-    files, tar = handle_tarfile_or_directory(data_dir)
 
-    if not files:
+    with TigerInput(data_dir) as tar:
+        if not tar:
             return
 
         with connect(dsn) as conn:
@@ -94,19 +118,12 @@ def add_tiger_data(data_dir, config, threads, tokenizer):
 
         with WorkerPool(dsn, place_threads, ignore_sql_errors=True) as pool:
             with tokenizer.name_analyzer() as analyzer:
-            for fname in files:
-                if not tar:
-                    fd = open(fname)
-                else:
-                    fd = io.TextIOWrapper(tar.extractfile(fname))
-
+                while tar:
+                    with tar.next_file() as fd:
                         handle_threaded_sql_statements(pool, fd, analyzer)
 
-                fd.close()
-
-    if tar:
-        tar.close()
         print('\n')
+
     LOG.warning("Creating indexes on Tiger data")
     with connect(dsn) as conn:
         sql = SQLPreprocessor(conn, config)