vidjil_utils: Search and traverse a JSON file

server/web2py/applications/vidjil/modules/vidjil_utils.py

 import math
 import re
 import defs
+import json
 from gluon import current
 from datetime import date
 
@@ -136,6 +137,53 @@ def search_first_regex_in_file(regex, filename, max_nb_line=None):
                 break
     return matched_keys
 
+
+#### Utilities on JSON
+
+def extract_value_from_json_path(json_path, json):
+    '''
+    Highly inspired from http://stackoverflow.com/a/7320664/1192742
+
+    Takes a path (for instance field1/field2/field3) and returns
+    the value at that path.
+
+    If the value doesn't exist None will be returned.
+    '''
+    elem = json
+    try:
+        for x in json_path.strip("/").split("/"):
+            elem = elem.get(x)
+    except:
+        pass
+
+    return elem
+
+def extract_fields_from_json(json_fields, pos_in_list, filename):
+    '''
+    Takes a map of JSON fields (the key is a common name
+    and the value is a path) and return a similar map
+    where the values are the values from the JSON filename.
+
+    If the value retrieved from a JSON is an array, we will
+    get only the item at position <pos_in_list>
+    '''
+    try:
+        json_dict = json.loads(open(filename).read())
+    except IOError:
+        json_dict = {}
+
+    matched_keys = {}
+    for field in json_fields:
+        value = extract_value_from_json_path(json_fields[field], json_dict)
+        if  not isinstance(value, basestring):
+            matched_keys[field] = value[pos_in_list]
+        else:
+            matched_keys[field] = value
+
+    return matched_keys
+
+####
+
 log_patient = re.compile('\((\d+)\)')
 log_config = re.compile(' c(\d+)')
 log_task = re.compile('\[(\d+)\]')