from datetime import datetime, date, time, timedelta

# dia de hoje menos 1 dia
d = date.today() - timedelta(days = 1)

# combina o dia com o horário meia-noite
startTimestamp = datetime.combine(d, time(0, 0)).timestamp()
# combina o dia com o horário 23:59
endTimestamp = datetime.combine(d, time(23, 59)).timestamp()

print(startTimestamp) # 1572231600.0
print(endTimestamp) # 1572317940.0