I have used Google Calendars to schedule and control a number of projects (eg.
sprinkler system, alarm clock, etc) . The following How To will get you started. You will of course need a google account.
Create Project
1) Start by visiting the
Google Developers Console
and
create a new project.
2) Select the project and navigate on the left menu to
APIs & auth then
APIs and
enable Calendar API for this project. You can disabled all other APIs if you only need Calendar access.
3) Next, select the
Consent screen menu option from the
APIs & auth menu. Enter a
Product Name and select an
Email Address. If you do not do this step, you will get a
Error: invalid_client error later on.
4) Next, select the
Credentials menu option from the
APIs & auth menu. Under
OAuth select
Create new Client ID.
5) For the
Create Client ID select
Installed application for
Application Type and select
Other for
Installed Application Type and finally click the
Create Client ID button.
6) After the ID has finished being created, click the
Download JSON button. Save and rename the file as something simple like
client_secret.json.
This json file contains your API credentials needed to access the Google Calendar APIs.
Install Google API Libraries
1) Install the Google API Libraries using Python's PIP installer:
$ sudo pip install --upgrade google-api-python-client
gflags may or may not be needed, depending on what code you use: (may be optional)
$ sudo pip install --upgrade python-gflags
If you would prefer alternatives, view the
Google APIs Client Library for Python page.
Authorize Application
Next we will need to run our application and authorize it against the desired account.
1) Clone my sample code:
# git clone https://github.com/oeey/gcalendar.git
The sample code is just a slight modification from the
Getting Started Sample Code. The Google sample code has some outdated code that will throw some obsoleted warnings.
2) The application has not been authorized to an account yet. Run the application once and you will be asked to paste a validation URL into your browser. Login to your desired target account (with the calendars you want to access) and then paste the validation URL into your browser.
For convenience I have a
first_auth.py script that is the same script as the
gcalendar.py script, but terminates after authorization. You can run any of the scripts to complete this authorization step.
The first_auth.py is pretty simple:
from apiclient.discovery import build
from oauth2client.file import Storage
from oauth2client.client import AccessTokenRefreshError
from oauth2client.client import OAuth2WebServerFlow
from oauth2client.tools import run_flow
from oauth2client.client import flow_from_clientsecrets
def main():
scope = 'https://www.googleapis.com/auth/calendar'
flow = flow_from_clientsecrets('client_secret.json', scope=scope)
storage = Storage('credentials.dat')
credentials = storage.get()
class fakeargparse(object): # fake argparse.Namespace
noauth_local_webserver = True
logging_level = "ERROR"
flags = fakeargparse()
if credentials is None or credentials.invalid:
credentials = run_flow(flow, storage, flags)
if __name__ == '__main__':
main()
You may notice the "
fakeargparse" code. The
run_flow() call wants the flags to be set from the parameters pulled from
argparse. I think that is overkill for what I needed, so I just created a fake container so
run_flow() wouldn't complain.
Run the
first_auth.py script to collect the application authorization.
$ python first_auth.py
Go to the following link in your browser:
https://accounts.google.com/o/oauth2/auth?scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fcalendar&redirect_uri=urn%3Aietf%3Awg%3Aoauth%3A2.0%3Aoob&response_type=code&client_id=1039XXXXXXXXXXXXXXXXXXXXXXXXXXcs46gdj2.apps.googleusercontent.com&access_type=offline
Enter verification code:
3) Copy the URL into the browser and accept the permissions.
4) You will be presented with a code, to which you will then enter back into the prompt of the first_auth.py application. The authorization will be stored in the
credentials.dat file for future requests.
$ python first_auth.py
Go to the following link in your browser:
https://accounts.google.com/o/oauth2/auth?scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fcalendar&redirect_uri=urn%3Aietf%3Awg%3Aoauth%3A2.0%3Aoob&response_type=code&client_id=46XXXXXXXXXX2-bXXXXXXXXXXXXXusvh6.apps.googleusercontent.com&access_type=offline
Enter verification code: 4/WzAQfXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX2vw2M2Pl7OykQI
Authentication successful.
Now that we have our API credentials and are authorized to access an account, we can begin to play with the Google Calendars.
View Upcoming Events
The
upcoming.py script builds off of the
first_auth.py script, cycles through the next few upcoming calendar events and displays the event titles.
...
if credentials is None or credentials.invalid:
credentials = run_flow(flow, storage, flags)
http = httplib2.Http()
http = credentials.authorize(http)
service = build('calendar', 'v3', http=http)
print "Upcoming Events:"
request = service.events().list(calendarId='primary')
while request != None:
response = request.execute()
for event in response.get('items', []):
print event.get('summary', 'NO SUMMARY')
request = service.events().list_next(request, response)
This script defaults to the
primary calendar associated with the account.
Calendar ID
The previous script defaults to the
primary calendar associated with the account. If you wish to specify an alternate calendar, you will need the Calendar ID. A calendar's ID can be found on the
Calendar Details setting page (same page you can change a calendar's name on). Look for the
Calendar Address line, and the
Calendar ID will be in the parenthesis. It will look something like "
a3sd5221ap2qe5ksbev3ip4@group.calendar.google.com".
Next 12 Hours of Events
Finally, to specify a time range for events, I use the following code in my
gcalendar.py script. This code will collect the next 12 hours worth of events.
...
service = build('calendar', 'v3', http=http)
# get the next 12 hours of events
epoch_time = time.time()
start_time = epoch_time - 3600 # 1 hour ago
end_time = epoch_time + 12 * 3600 # 12 hours in the future
tz_offset = - time.altzone / 3600
if tz_offset < 0:
tz_offset_str = "-%02d00" % abs(tz_offset)
else:
tz_offset_str = "+%02d00" % abs(tz_offset)
start_time = datetime.datetime.fromtimestamp(start_time).strftime("%Y-%m-%dT%H:%M:%S") + tz_offset_str
end_time = datetime.datetime.fromtimestamp(end_time).strftime("%Y-%m-%dT%H:%M:%S") + tz_offset_str
print "Getting calendar events between: " + start_time + " and " + end_time
events = service.events().list(calendarId='primary', timeMin=start_time, timeMax=end_time, singleEvents=True).execute()singleEvents=True).execute()
#pprint.pprint(events)
for event in events['items']:
print event["summary]
And this is the basis for the code I use to schedule my
sprinkler system with.
