Do Python modules load once and only once?

main.py

def main():
  print("Importing tell the time module")
  import tell_the_time
  print("Importing tell the time module again")
  import tell_the_time as tell_the_time_again

if __name__ == '__main__':
  main()

tell_the_time.py

from datetime import datetime

print(datetime.now())

Looks like modules are only imported once.

$ python --version
Python 2.7.12
$ python main.py 
Importing tell the time module
2017-01-31 11:01:06.000146
Importing tell the time module again
$ python3 --version
Python 3.5.2
$ python3 main.py 
Importing tell the time module
2017-01-31 11:01:16.400008
Importing tell the time module again