You can convert an Excel file to a Google Sheets file using the DRIVE API method Files: copy
You just need to know the fileId and specify the option convert=true.
Sample:
service.files().copy(fileId=file_id,convert=true, body={"title": "Chose a title"}).execute()
If your excel file is on your local disc - upload it to a Google Sheets file as following:
file_metadata = {
'name': 'Desired Name',
'mimeType': 'application/vnd.google-apps.spreadsheet'
}
media = MediaFileUpload('files/myExcelFile.xls',
mimetype='application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
resumable=True)
file = drive_service.files().create(body=file_metadata,
media_body=media,
fields='id').execute()
print 'The converted file is on your Google Drive and has the Id: %s' % file.get('id')
More information here and here.