Python BigQuery 属性错误：'Row'对象没有属性

Question

我有一个行对象row.total_bytes_processed，其中的行返回None。如果它返回None，我有逻辑将值默认为0

for row in rows:
if row.total_bytes_processed is  not None:
cost_dollars = (row.total_bytes_processed/1024 **4) *5
print( f"JOB_ID : {row.job_id} | Creation_Time : {row.creation_time} |  Query: {row.query} | Total_Bytes_processed : {row.total_bytes_processed} | Estimated_Cost : ${cost_dollars}".format(
row.job_id, row.creation_time, row.query, row.total_bytes_processed,cost_dollars))
else:
row.total_bytes_processed = 0 # <- Error occurs here
cost_dollars = (int(row.total_bytes_processed) / 1024 ** 4) * 5
print(f"JOB_ID : {row.job_id} | Creation_Time : {row.creation_time} |  Query: {row.query} | Total_Bytes_processed : {row.total_bytes_processed} | Estimated_Cost : ${cost_dollars}".format(row.job_id, row.creation_time, row.query, row.total_bytes_processed, cost_dollars))

然而，当我这样做时，我收到了这个错误：

row.total_bytes_processed = 0
AttributeError: 'Row' object has no attribute 'total_bytes_processed'

如何修复此错误？我可以不将None(Nonetype(默认为0吗？

我已经验证了所有行都已处理total_bytes_processed。

这是我的源代码：

from google.cloud import bigquery
from google.oauth2 import service_account

sql = """
SELECT
job_id,
creation_time,
user_email,
query,
total_bytes_processed
FROM `region-us`.INFORMATION_SCHEMA.JOBS_BY_PROJECT
WHERE project_id ='nj-dev-blah'
AND creation_time BETWEEN TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 183 DAY)
AND CURRENT_TIMESTAMP()
ORDER BY creation_time DESC
LIMIT 100
"""

query_job = client.query(sql)# Make an API request.
results = query_job.result()
rows = list(results)
print("The query data:")
# print(rows)
for row in rows:
if row.total_bytes_processed is  not None:
cost_dollars = (row.total_bytes_processed/1024 **4) *5
print( f"JOB_ID : {row.job_id} | Creation_Time : {row.creation_time} |  Query: {row.query} | Total_Bytes_processed : {row.total_bytes_processed} | Estimated_Cost : ${cost_dollars}".format(
row.job_id, row.creation_time, row.query, row.total_bytes_processed,cost_dollars))
else:
row.total_bytes_processed = 0
cost_dollars = (int(row.total_bytes_processed) / 1024 ** 4) * 5
print(f"JOB_ID : {row.job_id} | Creation_Time : {row.creation_time} |  Query: {row.query} | Total_Bytes_processed : {row.total_bytes_processed} | Estimated_Cost : ${cost_dollars}".format(row.job_id, row.creation_time, row.query, row.total_bytes_processed, cost_dollars))

Answer 1

如果使用，则具有等于"None"的属性与根本没有这样的属性是不同的

if row.total_bytes_processed is not None:

Python将尝试访问此对象的名为"total_bytes_processed"的属性，然后将其与None进行比较。出现此错误是因为在这种情况下，该对象的属性"total_bytes_processed"不存在。

您可以使用方法"hasattr"，提供对象和您要查找的属性的名称作为参数，如果参数存在，该方法将返回True，否则返回False：

if hasattr(row, "total_bytes_processed"):

请记住，即使该属性存在并等于"None"，"hasattr"仍将返回True，因此您可以将其作为外部验证，然后，在您知道该属性存在后，验证其是否等于"None"并采取相应行动。它可能类似于：

for row in rows:
if hasattr(row, "total_bytes_processed"):
if row.total_bytes_processed is not None:
cost_dollars = (row.total_bytes_processed/1024 **4) *5
print( f"JOB_ID : {row.job_id} | Creation_Time : {row.creation_time} |  Query: {row.query} | Total_Bytes_processed : {row.total_bytes_processed} | Estimated_Cost : ${cost_dollars}".format(
row.job_id, row.creation_time, row.query, row.total_bytes_processed,cost_dollars))
else:
row.total_bytes_processed = 0
cost_dollars = (int(row.total_bytes_processed) / 1024 ** 4) * 5
print(f"JOB_ID : {row.job_id} | Creation_Time : {row.creation_time} |  Query: {row.query} | Total_Bytes_processed : {row.total_bytes_processed} | Estimated_Cost : ${cost_dollars}".format(row.job_id, row.creation_time, row.query, row.total_bytes_processed, cost_dollars))
else:
#code for when total_bytes_processed does not exists