IVR: Phone Tree with Python and Flask

Learn to create an interactive voice response (IVR) system with Twilio Programmable Voice and your Python web application by using the <Gather>, <Say>, and <Dial> TwiML elements to handle phone tree logic inside an application. You can use this guide to send notifications, create self-service automation, build inbound call centers, build outbound call centers, or implement AI or ML transcription.

See Related reference documentation to learn more about the TwiML voice elements used in this guide.

This Python Flask sample application is modeled after a typical call center experience.

Stranded aliens can call a phone number and receive instructions on how to get out of earth safely, or call their home planet directly. In this tutorial, we'll show you the critical bits of code that make this work.

(information)

Info

To run this sample app yourself, download the code and follow the instructions on GitHub. You can also look at this GitHub repository to see how we've structured our application's file structure.

Read how Livestream and others built Interactive Voice Response with Twilio. Find source code for many web frameworks on our IVR tutorial page.

Answering a Phone Call

To initiate the phone tree, we need to configure one of our Twilio numbers to send our web application an HTTP request when we get an incoming call.

Click on one of your numbers and configure the Voice URL to point to our app. In our code, the route will be /ivr/welcome.

Twilio console showing IVR webhook configuration for phone number with HTTP POST method.

If you don't already have a server configured to use as your webhook, ngrok is an excellent tool for testing webhooks locally.

With our Twilio number configured, we are prepared to respond to the Twilio request.

Respond to the Twilio request with TwiML

Our Twilio number is now configured to send HTTP requests to this controller method on any incoming voice calls. Our app responds with TwiML to tell Twilio what to do in response to the message.

In this case, we tell Twilio to Gather the input from the caller and then Play a welcome message.

You may have noted we're using an unknown method, ``` TwiML` ``. This method comes from a custom view helper that takes a TwiML Response and transforms it into a valid HTTP Response. Check out the implementation:

1import flask
2
3def twiml(resp):
4    resp = flask.Response(str(resp))
5    resp.headers['Content-Type'] = 'text/xml'
6    return resp

Respond with TwiML to gather an option from the caller

ivr_phone_tree_python/views.py

1from flask import (
2    flash,
3    render_template,
4    redirect,
5    request,
6    session,
7    url_for,
8)
9from twilio.twiml.voice_response import VoiceResponse
10
11from ivr_phone_tree_python import app
12from ivr_phone_tree_python.view_helpers import twiml
13
14
15@app.route('/')
16@app.route('/ivr')
17def home():
18    return render_template('index.html')
19
20
21@app.route('/ivr/welcome', methods=['POST'])
22def welcome():
23    response = VoiceResponse()
24    with response.gather(
25        num_digits=1, action=url_for('menu'), method="POST"
26    ) as g:
27        g.say(message="Thanks for calling the E T Phone Home Service. " +
28              "Please press 1 for directions." +
29              "Press 2 for a list of planets to call.", loop=3)
30    return twiml(response)
31
32
33@app.route('/ivr/menu', methods=['POST'])
34def menu():
35    selected_option = request.form['Digits']
36    option_actions = {'1': _give_instructions,
37                      '2': _list_planets}
38
39    if option_actions.has_key(selected_option):
40        response = VoiceResponse()
41        option_actions[selected_option](response)
42        return twiml(response)
43
44    return _redirect_welcome()
45
46
47@app.route('/ivr/planets', methods=['POST'])
48def planets():
49    selected_option = request.form['Digits']
50    option_actions = {'2': "+19295566487",
51                      '3': "+17262043675",
52                      "4": "+16513582243"}
53
54    if selected_option in option_actions:
55        response = VoiceResponse()
56        response.dial(option_actions[selected_option])
57        return twiml(response)
58
59    return _redirect_welcome()
60
61
62# private methods
63
64def _give_instructions(response):
65    response.say("To get to your extraction point, get on your bike and go " +
66                 "down the street. Then Left down an alley. Avoid the police" +
67                 " cars. Turn left into an unfinished housing development." +
68                 "Fly over the roadblock. Go past the moon. Soon after " +
69                 "you will see your mother ship.",
70                 voice="Polly.Amy", language="en-GB")
71
72    response.say("Thank you for calling the E T Phone Home Service - the " +
73                 "adventurous alien's first choice in intergalactic travel")
74
75    response.hangup()
76    return response
77
78
79def _list_planets(response):
80    with response.gather(
81        numDigits=1, action=url_for('planets'), method="POST"
82    ) as g:
83        g.say("To call the planet Broh doe As O G, press 2. To call the " +
84              "planet DuhGo bah, press 3. To call an oober asteroid " +
85              "to your location, press 4. To go back to the main menu " +
86              " press the star key.",
87              voice="Polly.Amy", language="en-GB", loop=3)
88
89    return response
90
91
92def _redirect_welcome():
93    response = VoiceResponse()
94    response.say("Returning to the main menu", voice="Polly.Amy", language="en-GB")
95    response.redirect(url_for('welcome'))
96
97    return twiml(response)

To see the full layout of this app, you can check out its file structure in the GitHub repository.

After playing the audio and retrieving the caller's input, Twilio will send this input to our application.

Where to send the caller's input

The gather's action parameter takes an absolute or relative URL as a value - in our case, this is the menu endpoint.

When the caller finishes entering digits, Twilio will make a GET or POST request to this URL and include a Digits parameter with the number our caller chose.

After making its request, Twilio will continue the current call using the TwiML received in your response. Note that any TwiML verbs occurring after a <Gather> are unreachable unless the caller does not enter any digits.

Send caller input to the intended route

ivr_phone_tree_python/views.py

1from flask import (
2    flash,
3    render_template,
4    redirect,
5    request,
6    session,
7    url_for,
8)
9from twilio.twiml.voice_response import VoiceResponse
10
11from ivr_phone_tree_python import app
12from ivr_phone_tree_python.view_helpers import twiml
13
14
15@app.route('/')
16@app.route('/ivr')
17def home():
18    return render_template('index.html')
19
20
21@app.route('/ivr/welcome', methods=['POST'])
22def welcome():
23    response = VoiceResponse()
24    with response.gather(
25        num_digits=1, action=url_for('menu'), method="POST"
26    ) as g:
27        g.say(message="Thanks for calling the E T Phone Home Service. " +
28              "Please press 1 for directions." +
29              "Press 2 for a list of planets to call.", loop=3)
30    return twiml(response)
31
32
33@app.route('/ivr/menu', methods=['POST'])
34def menu():
35    selected_option = request.form['Digits']
36    option_actions = {'1': _give_instructions,
37                      '2': _list_planets}
38
39    if option_actions.has_key(selected_option):
40        response = VoiceResponse()
41        option_actions[selected_option](response)
42        return twiml(response)
43
44    return _redirect_welcome()
45
46
47@app.route('/ivr/planets', methods=['POST'])
48def planets():
49    selected_option = request.form['Digits']
50    option_actions = {'2': "+19295566487",
51                      '3': "+17262043675",
52                      "4": "+16513582243"}
53
54    if selected_option in option_actions:
55        response = VoiceResponse()
56        response.dial(option_actions[selected_option])
57        return twiml(response)
58
59    return _redirect_welcome()
60
61
62# private methods
63
64def _give_instructions(response):
65    response.say("To get to your extraction point, get on your bike and go " +
66                 "down the street. Then Left down an alley. Avoid the police" +
67                 " cars. Turn left into an unfinished housing development." +
68                 "Fly over the roadblock. Go past the moon. Soon after " +
69                 "you will see your mother ship.",
70                 voice="Polly.Amy", language="en-GB")
71
72    response.say("Thank you for calling the E T Phone Home Service - the " +
73                 "adventurous alien's first choice in intergalactic travel")
74
75    response.hangup()
76    return response
77
78
79def _list_planets(response):
80    with response.gather(
81        numDigits=1, action=url_for('planets'), method="POST"
82    ) as g:
83        g.say("To call the planet Broh doe As O G, press 2. To call the " +
84              "planet DuhGo bah, press 3. To call an oober asteroid " +
85              "to your location, press 4. To go back to the main menu " +
86              " press the star key.",
87              voice="Polly.Amy", language="en-GB", loop=3)
88
89    return response
90
91
92def _redirect_welcome():
93    response = VoiceResponse()
94    response.say("Returning to the main menu", voice="Polly.Amy", language="en-GB")
95    response.redirect(url_for('welcome'))
96
97    return twiml(response)

Now that we have told Twilio where to send the caller's input, we can look at how to process that input.

This route handles processing the caller's input.

If our caller chooses '1' for directions, we use the _give_instructions method to respond with TwiML that will Say directions to our caller's extraction point.

If the caller chooses '2' to call their home planet, then we need to gather more input from them. We wrote another method to handle this, _list_planets, which we'll cover in the next step.

If the caller enters anything else, we respond with a TwiML Redirect to the main menu.

ivr_phone_tree_python/views.py

1from flask import (
2    flash,
3    render_template,
4    redirect,
5    request,
6    session,
7    url_for,
8)
9from twilio.twiml.voice_response import VoiceResponse
10
11from ivr_phone_tree_python import app
12from ivr_phone_tree_python.view_helpers import twiml
13
14
15@app.route('/')
16@app.route('/ivr')
17def home():
18    return render_template('index.html')
19
20
21@app.route('/ivr/welcome', methods=['POST'])
22def welcome():
23    response = VoiceResponse()
24    with response.gather(
25        num_digits=1, action=url_for('menu'), method="POST"
26    ) as g:
27        g.say(message="Thanks for calling the E T Phone Home Service. " +
28              "Please press 1 for directions." +
29              "Press 2 for a list of planets to call.", loop=3)
30    return twiml(response)
31
32
33@app.route('/ivr/menu', methods=['POST'])
34def menu():
35    selected_option = request.form['Digits']
36    option_actions = {'1': _give_instructions,
37                      '2': _list_planets}
38
39    if option_actions.has_key(selected_option):
40        response = VoiceResponse()
41        option_actions[selected_option](response)
42        return twiml(response)
43
44    return _redirect_welcome()
45
46
47@app.route('/ivr/planets', methods=['POST'])
48def planets():
49    selected_option = request.form['Digits']
50    option_actions = {'2': "+19295566487",
51                      '3': "+17262043675",
52                      "4": "+16513582243"}
53
54    if selected_option in option_actions:
55        response = VoiceResponse()
56        response.dial(option_actions[selected_option])
57        return twiml(response)
58
59    return _redirect_welcome()
60
61
62# private methods
63
64def _give_instructions(response):
65    response.say("To get to your extraction point, get on your bike and go " +
66                 "down the street. Then Left down an alley. Avoid the police" +
67                 " cars. Turn left into an unfinished housing development." +
68                 "Fly over the roadblock. Go past the moon. Soon after " +
69                 "you will see your mother ship.",
70                 voice="Polly.Amy", language="en-GB")
71
72    response.say("Thank you for calling the E T Phone Home Service - the " +
73                 "adventurous alien's first choice in intergalactic travel")
74
75    response.hangup()
76    return response
77
78
79def _list_planets(response):
80    with response.gather(
81        numDigits=1, action=url_for('planets'), method="POST"
82    ) as g:
83        g.say("To call the planet Broh doe As O G, press 2. To call the " +
84              "planet DuhGo bah, press 3. To call an oober asteroid " +
85              "to your location, press 4. To go back to the main menu " +
86              " press the star key.",
87              voice="Polly.Amy", language="en-GB", loop=3)
88
89    return response
90
91
92def _redirect_welcome():
93    response = VoiceResponse()
94    response.say("Returning to the main menu", voice="Polly.Amy", language="en-GB")
95    response.redirect(url_for('welcome'))
96
97    return twiml(response)

If the caller chooses '2', we will take them to the Planet Directory to collect more input.

The Planet Directory: Collecting more input from the caller

If our callers choose to call their home planet, we will read them the planet directory. Our planet directory is similar to a typical "company directory" feature of most IVRs.

In our TwiML response, we again use a Gather verb to get our caller's input. This time, the action verb points to the planets route, which will map our response to what the caller chooses.

Let's look at that route next. The TwiML response we return for that route uses a Dial verb with the appropriate phone number to connect our caller to their home planet.

Collect more input from the caller via the Planet Directory

ivr_phone_tree_python/views.py

1from flask import (
2    flash,
3    render_template,
4    redirect,
5    request,
6    session,
7    url_for,
8)
9from twilio.twiml.voice_response import VoiceResponse
10
11from ivr_phone_tree_python import app
12from ivr_phone_tree_python.view_helpers import twiml
13
14
15@app.route('/')
16@app.route('/ivr')
17def home():
18    return render_template('index.html')
19
20
21@app.route('/ivr/welcome', methods=['POST'])
22def welcome():
23    response = VoiceResponse()
24    with response.gather(
25        num_digits=1, action=url_for('menu'), method="POST"
26    ) as g:
27        g.say(message="Thanks for calling the E T Phone Home Service. " +
28              "Please press 1 for directions." +
29              "Press 2 for a list of planets to call.", loop=3)
30    return twiml(response)
31
32
33@app.route('/ivr/menu', methods=['POST'])
34def menu():
35    selected_option = request.form['Digits']
36    option_actions = {'1': _give_instructions,
37                      '2': _list_planets}
38
39    if option_actions.has_key(selected_option):
40        response = VoiceResponse()
41        option_actions[selected_option](response)
42        return twiml(response)
43
44    return _redirect_welcome()
45
46
47@app.route('/ivr/planets', methods=['POST'])
48def planets():
49    selected_option = request.form['Digits']
50    option_actions = {'2': "+19295566487",
51                      '3': "+17262043675",
52                      "4": "+16513582243"}
53
54    if selected_option in option_actions:
55        response = VoiceResponse()
56        response.dial(option_actions[selected_option])
57        return twiml(response)
58
59    return _redirect_welcome()
60
61
62# private methods
63
64def _give_instructions(response):
65    response.say("To get to your extraction point, get on your bike and go " +
66                 "down the street. Then Left down an alley. Avoid the police" +
67                 " cars. Turn left into an unfinished housing development." +
68                 "Fly over the roadblock. Go past the moon. Soon after " +
69                 "you will see your mother ship.",
70                 voice="Polly.Amy", language="en-GB")
71
72    response.say("Thank you for calling the E T Phone Home Service - the " +
73                 "adventurous alien's first choice in intergalactic travel")
74
75    response.hangup()
76    return response
77
78
79def _list_planets(response):
80    with response.gather(
81        numDigits=1, action=url_for('planets'), method="POST"
82    ) as g:
83        g.say("To call the planet Broh doe As O G, press 2. To call the " +
84              "planet DuhGo bah, press 3. To call an oober asteroid " +
85              "to your location, press 4. To go back to the main menu " +
86              " press the star key.",
87              voice="Polly.Amy", language="en-GB", loop=3)
88
89    return response
90
91
92def _redirect_welcome():
93    response = VoiceResponse()
94    response.say("Returning to the main menu", voice="Polly.Amy", language="en-GB")
95    response.redirect(url_for('welcome'))
96
97    return twiml(response)

Again, we show some options to the caller and instruct Twilio to collect the caller's choice.

The Planet Directory: Connect the caller to another number

In this route, we grab the caller's digit selection from the HTTP request and store it in a variable called selected_option. We then use a Dial verb with the appropriate phone number to connect our caller to their home planet.

The current numbers are hardcoded, but you could update this code to read phone numbers from a database or a file.

Connect to another number based on caller input

ivr_phone_tree_python/views.py

1from flask import (
2    flash,
3    render_template,
4    redirect,
5    request,
6    session,
7    url_for,
8)
9from twilio.twiml.voice_response import VoiceResponse
10
11from ivr_phone_tree_python import app
12from ivr_phone_tree_python.view_helpers import twiml
13
14
15@app.route('/')
16@app.route('/ivr')
17def home():
18    return render_template('index.html')
19
20
21@app.route('/ivr/welcome', methods=['POST'])
22def welcome():
23    response = VoiceResponse()
24    with response.gather(
25        num_digits=1, action=url_for('menu'), method="POST"
26    ) as g:
27        g.say(message="Thanks for calling the E T Phone Home Service. " +
28              "Please press 1 for directions." +
29              "Press 2 for a list of planets to call.", loop=3)
30    return twiml(response)
31
32
33@app.route('/ivr/menu', methods=['POST'])
34def menu():
35    selected_option = request.form['Digits']
36    option_actions = {'1': _give_instructions,
37                      '2': _list_planets}
38
39    if option_actions.has_key(selected_option):
40        response = VoiceResponse()
41        option_actions[selected_option](response)
42        return twiml(response)
43
44    return _redirect_welcome()
45
46
47@app.route('/ivr/planets', methods=['POST'])
48def planets():
49    selected_option = request.form['Digits']
50    option_actions = {'2': "+19295566487",
51                      '3': "+17262043675",
52                      "4": "+16513582243"}
53
54    if selected_option in option_actions:
55        response = VoiceResponse()
56        response.dial(option_actions[selected_option])
57        return twiml(response)
58
59    return _redirect_welcome()
60
61
62# private methods
63
64def _give_instructions(response):
65    response.say("To get to your extraction point, get on your bike and go " +
66                 "down the street. Then Left down an alley. Avoid the police" +
67                 " cars. Turn left into an unfinished housing development." +
68                 "Fly over the roadblock. Go past the moon. Soon after " +
69                 "you will see your mother ship.",
70                 voice="Polly.Amy", language="en-GB")
71
72    response.say("Thank you for calling the E T Phone Home Service - the " +
73                 "adventurous alien's first choice in intergalactic travel")
74
75    response.hangup()
76    return response
77
78
79def _list_planets(response):
80    with response.gather(
81        numDigits=1, action=url_for('planets'), method="POST"
82    ) as g:
83        g.say("To call the planet Broh doe As O G, press 2. To call the " +
84              "planet DuhGo bah, press 3. To call an oober asteroid " +
85              "to your location, press 4. To go back to the main menu " +
86              " press the star key.",
87              voice="Polly.Amy", language="en-GB", loop=3)
88
89    return response
90
91
92def _redirect_welcome():
93    response = VoiceResponse()
94    response.say("Returning to the main menu", voice="Polly.Amy", language="en-GB")
95    response.redirect(url_for('welcome'))
96
97    return twiml(response)

Use cases for IVR phone trees with Twilio Programmable Voice

See use cases for IVRs with Twilio Programmable Voice to learn about the different applications you can build with IVR phone trees.

Result

After following this guide, you can successfully process incoming voice calls and present an interactive menu using Twilio Programmable Voice in your application. You will have a live IVR system capable of listening to dual-tone multi-frequency (DTMF) keypad inputs, executing logic conditionally based on user choice, and dynamically forwarding or terminating calls based on your response payload.

Next steps

Explore the following guides to build on what you've learned in this guide:

Respond to incoming phone calls: Learn how to handle incoming webhooks from Twilio to dynamically direct callers.
Collect payments during calls: Use the <Pay> TwiML verb to securely collect payment information from callers.
Make outbound phone calls: Initiate phone calls programmatically from your Node.js application.

IVR: Phone Tree with Python and Flask

Info

Answering a Phone Call

Respond to the Twilio request with TwiML

Respond with TwiML to gather an option from the caller

Where to send the caller's input

Send caller input to the intended route

The Main Menu: Processing the caller's selection

Main menu and return instructions

The Planet Directory: Collecting more input from the caller

Collect more input from the caller via the Planet Directory

The Planet Directory: Connect the caller to another number

Connect to another number based on caller input

Use cases for IVR phone trees with Twilio Programmable Voice

Result

Next steps