[Python] Python time-interval check returns None when two lecture intervals share the same...

I’m building an attendance system in Python where lecture timings come from a MySQL table:

day | start | end
----+------------+-----------
Mon | 10:00:00 | 10:45:00
Mon | 10:45:00 | 11:30:00
...


My goal is:

1. 
   Fetch today’s lecture timings from the database
   
   
2. 
   Continuously check the current time
   
   
3. 
   Start face-detection automatically only during the active lecture
   
   
4. 
   Keep waiting (not exit) when no lecture is active yet
   

I am currently doing this

conn = mysql.connector.connect(...)
cursor = conn.cursor()
cursor.execute("SELECT start, end FROM timetable WHERE day=%s", ("Mon",))
rows = cursor.fetchall()

lectures = []
for s, e in rows:
start = datetime.combine(date.today(), s)
end = datetime.combine(date.today(), e)
lectures.append((start, end))

def get_current_lecture():
now = datetime.now()
for start, end in lectures:
if start <= now < end:
return (start, end)
return None

while True:
current = get_current_lecture()
if current is None:
break # <-- problem
else:
run_face_detection_until(current[1])


The problem:
If I start the script before the first lecture starts, get_current_lecture() returns None and the loop exits immediately.
But I need the script to wait and keep checking until the lecture actually starts, instead of stopping.

Question:
What is the correct way to integrate database-based time intervals with a Python loop so that:

• 
  the script runs continuously
  
  
• 
  returns None when idle
  
  
• 
  but does NOT exit the program
  
  
• 
  and automatically starts processing when the lecture time arrives?
  

Should I redesign the loop, or is there a better pattern for time-based scheduling with database intervals?

Continue reading...