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--- dev:index [2015/08/20 00:50] – kobe
+++ dev:index [2021/09/02 14:38] (current) – aggiunta problematica di conversione timestamps feroda
@@ Line 4: / Line 4: @@
   * [[dev:training|Training]]
-  * [[release-management|Release Management]]
   * [[git-forking-workflow|Git Forking Workflow]]
+  * [[release-management|Release Management]]
+  * [[coding-styleguide|Coding Styleguide]]
+====== Ora qui appunto sul tempo e python... ======
+Parliamo della conversione tra Unix Timestamp e Date time con Timezone, in Django e in SQL.
+Output di un codice di test nella piattaforma ''my-iot-framework'':
+<code>
+---
+Testing timestamps datetime conversions..
+UNIX TIMESTAMP ts = 1
+---
+[UNAWARE] fromtimestamp = dtunaware = datetime.datetime(1970, 1, 1, 1, 0, 1)
+[UNAWARE] dtunaware.strftime("%s") = '1'
+[UNAWARE] defaultfilters.date(dtunaware, "U") = '1'
+[UNAWARE] EXTRACT EPOCH dtunaware_metrics[0]["ts"] = 3601
+---
+[AWARE] fromtimestamp.replace(tzinfo=UTC): dtaware = datetime.datetime(1970, 1, 1, 1, 0, 1, tzinfo=<UTC>)
+[AWARE] dtaware.strftime("%s") = '1'
+[AWARE] defaultfilters.date(dtaware, "U") = '3601'
+[AWARE] EXTRACT EPOCH dtaware_metrics[0]["ts"] = 7201
+---
+[UTC] utcfromtimestamp: utcdt = datetime.datetime(1970, 1, 1, 0, 0, 1)
+[UTC] utcdt.strftime("%s") = '-3599'
+[UTC] defaultfilters.date(utcdt, "U") = '-3599'
+[UTC] EXTRACT EPOCH utcdt_metrics[0]["ts"] = 1
+</code>
+Codice per riprodurre questo output nella shell Django ''manage.py shell'':
+<code>
+from datetime import datetime
+import pytz
+from django.template import defaultfilters
+from django.db.models.functions import Extract
+from web.models import Board
+from web.models.metrics import get_board_metric_model
+ts = 1
+dtunaware = datetime.fromtimestamp(ts)
+dtaware = datetime.fromtimestamp(ts).replace(tzinfo=pytz.UTC)
+utcdt = datetime.utcfromtimestamp(ts)
+board = Board.objects.first()
+m = get_board_metric_model(board)
+m.objects.create(time=utcdt, data={})
+m.objects.create(time=dtaware, data={})
+m.objects.create(time=dtunaware, data={})
+dtunaware_metrics = m.objects.filter(time=dtunaware).annotate(ts=Extract("time", "epoch")).values()
+dtaware_metrics = m.objects.filter(time=dtaware).annotate(ts=Extract("time", "epoch")).values()
+utcdt_metrics = m.objects.filter(time=utcdt).annotate(ts=Extract("time", "epoch")).values()
+print("---")
+print(f"Testing timestamps datetime conversions..")
+print(f"UNIX TIMESTAMP {ts = }")
+print("---")
+print(f"[UNAWARE] fromtimestamp = {dtunaware = }")
+print(f'[UNAWARE] {dtunaware.strftime("%s") = }')
+print(f'[UNAWARE] {defaultfilters.date(dtunaware, "U") = }')
+print(f'[UNAWARE] EXTRACT EPOCH {dtunaware_metrics[0]["ts"] = }')
+print("---")
+print(f"[AWARE] fromtimestamp.replace(tzinfo=UTC): {dtaware = }")
+print(f'[AWARE] {dtaware.strftime("%s") = }')
+print(f'[AWARE] {defaultfilters.date(dtaware, "U") = }')
+print(f'[AWARE] EXTRACT EPOCH {dtaware_metrics[0]["ts"] = }')
+print("---")
+print(f"[UTC] utcfromtimestamp: {utcdt = }")
+print(f'[UTC] {utcdt.strftime("%s") = }')
+print(f'[UTC] {defaultfilters.date(utcdt, "U") = }')
+print(f'[UTC] EXTRACT EPOCH {utcdt_metrics[0]["ts"] = }')
+</code>
+Benedette siano le f-strings per il debug!