pip install yapsl

from yapsl import SmsType, SmsGateway

gw = SmsGateway('/dev/ttyUSB0', verbose=False) # verbose=True is mostly for debugging purposes:
                                               # it'll show the complete communication with the modem
                                               # (plus some more logs)

# Optional: It's possible to check if the modem is connected to a network (this is as well always done when sending an SMS)
if not gw.is_connected():
    print("Not connected!")
    print("Auto select network")
    gw.auto_select_network()
    sleep(60)

# send an ordinary SMS
gw.send('0786391538', 'this is a test message')

# send a "flash"-SMS (this is usually a popup and by default these SMS are not stored)
gw.send('0786391538', 'this is a test message', flash=True)

# send a silent SMS (text wont be shown: this is just some kind of 'ping')
gw.send('0786391538', 'this is a test message', type=SmsType.TYPE_0)

# send a replaceable SMS (note there exist only 7 of these replaceable SMS)
gw.send('0786391538', '3...', type=SmsType.REPLACE_TYPE_1)

# replace the previous sent SMS (a few times)
gw.send('0786391538', '2...', type=SmsType.REPLACE_TYPE_1)
gw.send('0786391538', '1...', type=SmsType.REPLACE_TYPE_1)
gw.send('0786391538', 'Hey:D', type=SmsType.REPLACE_TYPE_1)