Usage

Integrating pycall into your project is quick and easy! After reading through the sections below, you should be able to integrate pycall into your project, and understand what it can and cannot be used for.

Preparation

The rest of this guide assumes you have the following:

1. A working Asterisk server.
2. Some sort of PSTN (public switch telephone network) connectivity. Regardless of what sort of PSTN connection you have (SIP / DAHDI / ZAPTEL / ISDN / etc.), as long as you can make calls, you’re fine.

For simplicity’s sake, I’m going to assume for the rest of this guide that you have a SIP trunk named flowroute defined.

Hello, World!

pycall allows you to build applications that automate outbound calling. In the example below, we’ll call a phone number specified on the command line, say “hello world”, then hang up!

import sys
from pycall import CallFile, Call, Application

def call(number):
        c = Call('SIP/flowroute/%s' % number)
        a = Application('Playback', 'hello-world')
        cf = CallFile(c, a)
        cf.spool()

if __name__ == '__main__':
        call(sys.argv[1])

Just save the code above in a file named call.py and run it with python!

$ python call.py 18002223333

Assuming your Asterisk server is setup correctly, your program just placed a call to the phone number 18002223333, and said “hello world” to the person who answered the phone!

Code Breakdown

1. First we imported the pycall classes. The CallFile class allows us to make call files. The Call class stores information about a specific call, and the Application class lets us specify an Asterisk application as our Action. Every call file requires some sort of action (what do you want to do when the caller answers?).
2. Next, we build a Call object, and specify the phone number to call in standard Asterisk format. This tells Asterisk who to call.

Note

In this example we made a call out of a SIP trunk named flowroute, but you can specify any sort of dial string in its place. You can even tell Asterisk to call multiple phone numbers at once by separating your dial strings with the & character (eg: Local/1000@internal&SIP/flowroute/18002223333).

3. Then we build an Application object that tells Asterisk what to do when the caller answers our call. In this case, we tell Asterisk to run the Playback command, and pass the argument ‘hello-world’ to it.

Note

The name ‘hello-world’ here refers to one of the default Asterisk sound files that comes with all Asterisk installations. This file can be found in the directory /var/lib/asterisk/sounds/en/ on most systems.

4. Finally, we create the actual CallFile object, and run its spool() method to have Asterisk make the call.

Scheduling a Call in the Future

Let’s say you want to have Asterisk make a call at a certain time in the future–no problem. The spool() method allows you to specify an optional datetime object to tell Asterisk when you want the magic to happen.

In this example, we’ll tell Asterisk to run the call in exactly 1 hour:

import sys
from datetime import datetime
from datetime import timedelta
from pycall import CallFile, Call, Application

def call(number, time=None):
        c = Call('SIP/flowroute/%s' % number)
        a = Application('Playback', 'hello-world')
        cf = CallFile(c, a)
        cf.spool(time)

if __name__ == '__main__':
        call(sys.argv[1], datetime.now()+timedelta(hours=1))

Note

If you specify a value of None, the call file will be ran immediately.

Just for the heck of it, let’s look at one more code snippet. This time we’ll tell Asterisk to run the call file at exactly 1:00 AM on December 1, 2010.

import sys
from datetime import datetime
from pycall.callfile import CallFile

def call(number, time=None):
        c = Call('SIP/flowroute/%s' % number)
        a = Application('Playback', 'hello-world')
        cf = CallFile(c, a)
        cf.spool(time)

if __name__ == '__main__':
        call(sys.argv[1], datetime(2010, 12, 1, 1, 0, 0))

Setting Call File Permissions

In most environments, Asterisk is installed and ran as the user / group ‘asterisk’, which often poses a problem if your application doesn’t run under the ‘asterisk’ user account.

pycall recognizes that this is a frustrating problem to deal with, and provides three mechanisms for helping make permissions as painless as possible: the user attribute, the NoUserError, and the NoUserPermissionError.

• The user attribute lets you specify a system username that your call file should be ran as. For example, if your application is running as ‘root’, you could say:

  cf = CallFile(c, a, user='asterisk')
  

  and pycall would chown the call file to the ‘asterisk’ user before spooling.

• If you specify the user attribute, but the user doesn’t exist, pycall will raise the NoUserError so you know what’s wrong.

• Lastly, if your application doesn’t have the proper permissions to change the ownership of your call file, pycall will raise the NoUserPermissionError.

As an example, here we’ll change the call file permissions so that Asterisk can actually read our call file:

import sys
from pycall import CallFile, Call, Application

def call(number):
        c = Call('SIP/flowroute/%s' % number)
        a = Application('Playback', 'hello-world')
        cf = CallFile(c, a, user='asterisk')
        cf.spool(time)

if __name__ == '__main__':
        call(sys.argv[1])

Note

If you run this code on a system that doesn’t have Asterisk installed, you will most likely get a NoUserError since pycall won’t be able to find the ‘asterisk’ user that it’s trying to grant permissions to.

Adding Complex Call Logic

Most applications you write will probably be a bit more complex than “hello world”. In the example below, we’ll harness the power of the Context class to instruct Asterisk to run some custom dial plan code after the caller answers.

from pycall import CallFile, Call, Context

c = Call('SIP/flowroute/18002223333')
con = Context('survey', 's', '1')
cf = CallFile(c, con)
cf.spool()

For example purposes, let’s assume that somewhere in your Asterisk extensions.conf file there exists some dial plan in a context labeled survey.

After the caller answers our call, Asterisk will immediately jump to the dial plan code we’ve specified at survey,s,1 and start executing as much logic as desired.

Setting a CallerID

A lot of the time, you’ll want to force Asterisk to assume a specific caller ID when making outbound calls. To do this, simply specify a value for the callerid attribute:

c = Call('SIP/flowroute/18002223333', callerid="'Test User' <5555555555>'")

Now, when Asterisk makes your call, the person receiving the call (depending on their phone and service type) should see a call coming from “Test User” who’s phone number is 555-555-5555!

Passing Variables to Your Dial Plan

Often times, when building complex applications, you’ll want to pass specific data from your application to Asterisk, so that you can read the information later.

The example below will pass some information to our Asterisk dial plan code, so that it can use the information in our call.

from pycall import CallFile, Call, Context

vars = {'greeting': 'tt-monkeys'}

c = Call('SIP/flowroute/18882223333', variables=vars)
x = Context('survey', 's', '1')
cf = CallFile(c, x)
cf.spool()

And somewhere in our extensions.conf file...

[survey]
exten => s,1,Playback(${greeting})
exten => s,n,Hangup()

As you can see, our dial plan code can now access the variable ‘greeting’ and its value.

Track Your Calls with Asterisk Account Codes

Asterisk call files allow you to specify that a certain call should be associated with a certain account. This is mainly useful for logging purposes. This example logs the call with the ‘randall’ account:

c = Call('SIP/flowroute/18002223333', account='randall')

Note

For more information on call logs, read the CDR documentation.

Specify Call Timing Values

pycall provides several ways to control the timing of your calls.

1. wait_time lets you specify the amount of time to wait (in seconds) for the caller to answer before we consider our call attempt unsuccessful.
2. retry_time lets you specify the amount of time to wait (in seconds) between retries. Let’s say you try to call the number 1-800-222-3333 but they don’t answer, Asterisk will wait for retry_time seconds before calling the person again.
3. max_retries lets you specify the maximum amount of retry attempts (you don’t want to call someone forever, do you?).

Using these attributes is simple:

c = Call('SIP/flowroute/18002223333', wait_time=10, retry_time=60,
                max_retries=2)

Archiving Call Files

If, for some reason, you want to archive call files that have already been spooled with Asterisk, just set the archive attribute to True:

cf = CallFile(..., archive=True)

and Asterisk will copy the call file (with a status code) to the archive directory (typically /var/spool/asterisk/outgoing_done).

Dealing with Non-Standard Asterisk Installs

If your Asterisk server isn’t installed with the defaults, chances are you need to make some changes. pycall provides a ton of flexibility in this regard, so you should have no problems getting things running.

Specifying a Specific Name for Call Files

If you need to name your call file something special, just specify a value for both the filename and tempdir attributes:

cf = CallFile(..., filename='test.call', tempdir='/tmp')

Note

By default, pycall will randomly generate a call file name.

Specifing a Custom Spooling Directory

If you’re Asterisk install doesn’t spool to the default /var/spool/asterisk/outgoing directory, you can override it with the spool_dir attribute:

cf = CallFile(..., spool_dir='/tmp/outgoing')