BigQuery Python API - Not able to authenticate using user - google-bigquery

Question

I have a project owner permission on bigquery. And I able to create/delete/insert records into bigqquery table from UI.
However, when I am trying from Python, I am getting following error.
{
"error": {
"code": 401,
"message": "Request is missing required authentication credential. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.",
"errors": [
{
"message": "Login Required.",
"domain": "global",
"reason": "required",
"location": "Authorization",
"locationType": "header"
}
],
"status": "UNAUTHENTICATED",
"details": [
{
"#type": "type.googleapis.com/google.rpc.ErrorInfo",
"reason": "CREDENTIALS_MISSING",
"domain": "googleapis.com",
"metadata": {
"method": "google.cloud.bigquery.v2.JobService.ListJobs",
"service": "bigquery.googleapis.com"
}
}
]
}
}
Following is my code
def insert_data():
client = bigquery.Client()
job_config = bigquery.LoadJobConfig(
write_disposition=bigquery.WriteDisposition.WRITE_TRUNCATE,
source_format=bigquery.SourceFormat.CSV,
skip_leading_rows=1,
)
uri = " gs://xxx/csv_files/csv_test.csv"
table_id="xxx.Gaurang.csv_data"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.

Answer 1

You must authenticate when you use Google's libraries; Cloud Console and gcloud authentication does not extend transparently to code using the libraries.
Google's documentation is comprehensive and an example is here:
https://cloud.google.com/bigquery/docs/reference/libraries
Generally code run as a Service Account; the Service Account provides an identity and -- with Google Cloud services -- IAM provides roles/permissions based access, see BigQuery: access control with IAM.
Google provides a mechanism called Application Default Credentials that facilitates running code as a Service Account.