# Copyright 2018 Google LLC

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

# [START gmail_quickstart]

import os.path

from google.auth.transport.requests import Request

from google.oauth2.credentials import Credentials

from google_auth_oauthlib.flow import InstalledAppFlow

from googleapiclient.discovery import build

from googleapiclient.errors import HttpError

# If modifying these scopes, delete the file token.json.

SCOPES = ["https://www.googleapis.com/auth/gmail.readonly"]

def main():

"""Shows basic usage of the Gmail API.

Lists the user's Gmail labels.

"""

creds = None

# The file token.json stores the user's access and refresh tokens, and is

# created automatically when the authorization flow completes for the first

# time.

if os.path.exists("token.json"):

creds = Credentials.from_authorized_user_file("token.json", SCOPES)

# If there are no (valid) credentials available, let the user log in.

if not creds or not creds.valid:

if creds and creds.expired and creds.refresh_token:

creds.refresh(Request())

else:

flow = InstalledAppFlow.from_client_secrets_file(

"credentials.json", SCOPES

)

creds = flow.run_local_server(port=0)

# Save the credentials for the next run

with open("token.json", "w") as token:

token.write(creds.to_json())

try:

# Call the Gmail API

service = build("gmail", "v1", credentials=creds)

results = service.users().labels().list(userId="me").execute()

labels = results.get("labels", [])

if not labels:

print("No labels found.")

return

print("Labels:")

for label in labels:

print(label["name"])

except HttpError as error:

# TODO(developer) - Handle errors from gmail API.

print(f"An error occurred: {error}")

if __name__ == "__main__":

main()

# [END gmail_quickstart]