Google API Oauth Authorization code with PKCE Flow

google_pkce_flow.py

def base64URLEncode(random_bytes):
    return base64.urlsafe_b64encode(random_bytes)

def usha256(buffer):
    return sha256(buffer).digest()


client_id = 'your-client-id'
client_secret = 'your-client-secret'
redirect_uri = 'your-redirect-uri'
secret_data = b'your-secret-data'
random_chars = os.urandom(32)
verifier = base64URLEncode(secret_data).rstrip(b'=')
code_challenge = base64URLEncode(usha256(verifier)).rstrip(b'=')
code_challenge_method = "S256" 
scope = 'email openid profile'
oauth_resp = requests.get('https://accounts.google.com/o/oauth2/v2/auth', params={
    'client_id': client_id,
    'redirect_uri': redirect_uri,
    'response_type': 'code',
    'scope': scope,
    'code_challenge': code_challenge,
    'code_challenge_method': code_challenge_method
})

print(oauth_resp.url)
# From the print url there would be a parameter code=...... , 
# copy that code and paste in the input below 
code = input('enter code obtained: ')
authorization_url = oauth_resp.url
headers = {'Content-type': 'application/x-www-form-urlencoded'}
token_url = 'https://www.googleapis.com/oauth2/v4/token'
data = {
    'code': code,
    'client_id': client_id,
    'client_secret': client_secret,
    'redirect_uri': redirect_uri,
    'grant_type': 'authorization_code',
    'code_verifier': verifier
}
token_resp = requests.post(token_url, data=data, headers=headers)
# access token , refresh token , token expiration are the data here
# which can be used further to access the user information
print(token_resp)