Implements download cache for structure files

download.py

@@ -93,7 +93,7 @@ def download_topics(topics_url, topics_codes, target_dir: Path):
             zip_data.extractall(str(topic_dir))
 
 
-def download_structures(structure_url, ds_codes, target_dir: Path):
+def download_structures(structure_url, ds_codes, target_dir: Path, cache=True):
     """ Downloads each structure information structures folder """
     structure_dir = target_dir / 'structures'
     if not structure_dir.exists():
@@ -101,9 +101,13 @@ def download_structures(structure_url, ds_codes, target_dir: Path):
 
     log.info('Downloading structures...')
     for code in ds_codes:
+        structure_filepath = structure_dir / '{}.xml'.format(code)
+        if cache and structure_filepath.exists():
+            log.info('already downloaded.')
+            continue
+
         log.info('Downloading structure [{}]...'.format(code))
         r = requests.get(structure_url + code)
-        structure_filepath = structure_dir / '{}.xml'.format(code)
         with structure_filepath.open('wb') as fd:
             fd.write(r.content)