http://maluta.github.io/blog/at-commands/

at-cmd.py

#!/usr/bin/python 
import serial
import re
import time

device="/dev/ttyACM0" # modem interface

class Modem:

    def __init__(self):
        try:
            file = open(device, "r")
        except IOError:
            print "could not opem modem interface: ", device
            exit()
        self.ser=serial.Serial(device,19200,timeout=3)
        self.ser.write("ATZ\r")
        line=self.ser.read(10)

    def readuntil(self,word):
        ol=[]
        while 1:
            c=self.ser.read()
            if not c:
                break
            ol.append(c)
            ostring="".join(ol)
            if len(ol)>len(word)+1 and ostring[-4:]=="%s\r\n" % word:
                break
        return ostring

    def cmd(self,cmd):
        self.ser.write(cmd+"\r")
        r=self.readuntil("OK")
        r=r.split("\n")
        for i in range(len(r)):
            r[i]=r[i][:-1]
        return r

    def close(self):
        self.ser.close()


if __name__ == "__main__":

    m = Modem()

    AT_LIST = ["AT+CFUN?","AT+CPIN?","AT+CIMI","AT+CGSN","AT+CREG?","AT+COPS?","ATD+97314686;"]

    for cmd in AT_LIST:
        print m.cmd(cmd)[1]
        time.sleep(1)

    time.sleep(15) # wait and then end call
    m.cmd("ATZ")[1]

    m.close()