First version of parser and basic stats

main.py

@@ -0,0 +1,16 @@
+#! /usr/bin/env python3
+from datetime import datetime
+from pathlib import Path
+
+from parse import parse, wiki_stats
+
+
+def print_wiki_stats(filename: str) -> None:
+    path = Path(filename)
+    timestamp = datetime.fromtimestamp(path.stat().st_ctime)
+    print(f"Stand: {timestamp.strftime('%d.%m.%Y %H:%m Uhr')}")
+    print(wiki_stats(*parse(path)))
+
+
+if __name__ == "__main__":
+    print_wiki_stats("koma89_pretixdata.json")

parse.py

@@ -0,0 +1,58 @@
+import json
+from pathlib import Path
+from typing import Dict, Tuple, Union  # I have just python3.8 here :(
+
+
+def parse(filename: Union[str, Path]) -> Tuple[
+    Dict[int, str],
+    Dict[int, int],
+    Dict[int, str],
+    Dict[int, Dict[Tuple[int, str], int]]
+]:
+    """Parse a JSON export from pretix.
+
+    :param filename: filename of the JSON export to parse.
+    :returns: Four mappings:
+        * item_id to item name
+        * item_id to order count of this item
+        * question_id to question identifier
+        * question_id to stats for this question, which identifies an answer by its item_id and actual answer.
+            The stats map this identifier to number of occurrences
+    """
+    with open(filename, 'r', encoding='utf8') as f:
+        data = json.load(f)['event']
+
+    items = {i['id']: i['name'] for i in data['items']}
+    count_items = {id_: 0 for id_ in items}
+    questions = {q['id']: q['identifier'] for q in data['questions']}
+    quest_answers = {id_: {} for id_ in questions}
+
+    for order in data['orders']:
+        for position in order['positions']:
+            item_id = position['item']
+            count_items[item_id] += 1
+            for answer in position['answers']:
+                quest_id = answer['question']
+                answer_key = (item_id, answer['answer'])
+                quest_answers[quest_id][answer_key] = (
+                        quest_answers[quest_id].get(answer_key, 0) + 1
+                )
+
+    return items, count_items, questions, quest_answers
+
+
+def wiki_stats(items: Dict[int, str], count_items: Dict[int, int], questions: Dict[int, str],
+               quest_answers: Dict[int, Dict[Tuple[int, str], int]]) -> str:
+    """Generate stats for the Wiki page.
+
+    Input parameters are output of the parse() function.
+    """
+    ret = ""
+    ret += ('== Anmeldezahlen ==\n'
+            '{|class="wikitable sortable"\n'
+            '! Posten !! Anzahl\n'
+            '|-\n')
+    for item_id, item_name in items.items():
+        ret += f"|| {item_name} || {count_items.get(item_id)}\n|-\n"
+    ret += "|}\n"
+    return ret