处理 Python 中缺少非空断言运算符的问题

如何解决处理 Python 中缺少非空断言运算符的问题

我想允许 Mypy 的 strict_optional 标志。但是，请考虑：

2021-02-02 17:49:44.943933: I tensorflow/core/profiler/rpc/client/capture_profile.cc:198] Profiler delay_ms was 0,start_timestamp_ns set to 1612288184943887718 [2021-02-02T17:49:44.943887718+00:00]
Starting to trace for 20000 ms. Remaining attempt(s): 2
2021-02-02 17:49:44.944037: I tensorflow/core/profiler/rpc/client/remote_profiler_session_manager.cc:75] Deadline set to 2021-02-02T17:50:44.890124419+00:00 because max_session_duration_ms was 60000 and session_creation_timestamp_ns was 1612288184890124419 [2021-02-02T17:49:44.890124419+00:00]
2021-02-02 17:49:44.944197: I tensorflow/core/profiler/rpc/client/profiler_client.cc:113] Asynchronous gRPC Profile() to localhost:6009
2021-02-02 17:49:44.944316: I tensorflow/core/profiler/rpc/client/remote_profiler_session_manager.cc:96] Issued Profile gRPC to 1 clients
2021-02-02 17:49:44.944340: I tensorflow/core/profiler/rpc/client/profiler_client.cc:131] Waiting for completion.
2021-02-02 17:49:44.946274: I tensorflow/core/profiler/lib/profiler_session.cc:136] Profiler session initializing.
2021-02-02 17:49:44.947547: W tensorflow/core/profiler/lib/profiler_session.cc:144] Profiling is late (2021-02-02T17:49:44.946338176+00:00) for the scheduled start (2021-02-02T17:49:44.943887718+00:00) and will start immediately.
2021-02-02 17:49:44.947582: I tensorflow/core/profiler/lib/profiler_session.cc:155] Profiler session started.
2021-02-02 17:49:44.947660: I tensorflow/core/profiler/internal/gpu/cupti_tracer.cc:1365] Profiler found 2 GPUs
2021-02-02 17:49:44.949656: I tensorflow/stream_executor/platform/default/dso_loader.cc:49] Successfully opened dynamic library libcupti.so.11.0
2021-02-02 17:50:08.435260: I tensorflow/core/profiler/lib/profiler_session.cc:71] Profiler session collecting data.
2021-02-02 17:50:08.435591: I tensorflow/core/profiler/internal/gpu/cupti_tracer.cc:1487] CUPTI activity buffer flushed
2021-02-02 17:50:08.635192: I tensorflow/core/profiler/internal/gpu/cupti_collector.cc:228]  GpuTracer has collected 0 callback api events and 0 activity events. 
2021-02-02 17:50:08.648616: I tensorflow/core/profiler/rpc/profiler_service_impl.cc:67] Collecting XSpace to repository: ./logs/tbc_log/plugins/profile/2021_02_02_17_49_44/localhost_6009.xplane.pb
2021-02-02 17:50:08.650309: I tensorflow/core/profiler/lib/profiler_session.cc:172] Profiler session tear down.
2021-02-02 17:50:08.650676: W tensorflow/core/profiler/rpc/client/capture_profile.cc:133] No trace event is collected from localhost:6009
No trace event is collected. Automatically retrying.

2021-02-02 17:50:08.651046: I tensorflow/core/profiler/rpc/client/capture_profile.cc:198] Profiler delay_ms was 0,start_timestamp_ns set to 1612288208651017638 [2021-02-02T17:50:08.651017638+00:00]
Starting to trace for 20000 ms. Remaining attempt(s): 1
2021-02-02 17:50:08.651123: I tensorflow/core/profiler/rpc/client/remote_profiler_session_manager.cc:75] Deadline set to 2021-02-02T17:50:44.890124419+00:00 because max_session_duration_ms was 60000 and session_creation_timestamp_ns was 1612288184890124419 [2021-02-02T17:49:44.890124419+00:00]
2021-02-02 17:50:08.651274: I tensorflow/core/profiler/rpc/client/profiler_client.cc:113] Asynchronous gRPC Profile() to localhost:6009
2021-02-02 17:50:08.651391: I tensorflow/core/profiler/rpc/client/remote_profiler_session_manager.cc:96] Issued Profile gRPC to 1 clients
2021-02-02 17:50:08.651420: I tensorflow/core/profiler/rpc/client/profiler_client.cc:131] Waiting for completion.
2021-02-02 17:50:08.652492: I tensorflow/core/profiler/lib/profiler_session.cc:136] Profiler session initializing.
2021-02-02 17:50:08.652570: W tensorflow/core/profiler/lib/profiler_session.cc:144] Profiling is late (2021-02-02T17:50:08.652539729+00:00) for the scheduled start (2021-02-02T17:50:08.651017638+00:00) and will start immediately.
2021-02-02 17:50:08.652591: I tensorflow/core/profiler/lib/profiler_session.cc:155] Profiler session started.
2021-02-02 17:50:31.280828: I tensorflow/core/profiler/lib/profiler_session.cc:71] Profiler session collecting data.
2021-02-02 17:50:31.281134: I tensorflow/core/profiler/internal/gpu/cupti_tracer.cc:1487] CUPTI activity buffer flushed
2021-02-02 17:50:31.510697: I tensorflow/core/profiler/internal/gpu/cupti_collector.cc:228]  GpuTracer has collected 0 callback api events and 0 activity events. 
2021-02-02 17:50:31.515475: I tensorflow/core/profiler/rpc/profiler_service_impl.cc:67] Collecting XSpace to repository: ./logs/tbc_log/plugins/profile/2021_02_02_17_49_44/localhost_6009.xplane.pb
2021-02-02 17:50:31.518037: I tensorflow/core/profiler/lib/profiler_session.cc:172] Profiler session tear down.
2021-02-02 17:50:31.518440: W tensorflow/core/profiler/rpc/client/capture_profile.cc:133] No trace event is collected from localhost:6009
No trace event is collected. Automatically retrying.

2021-02-02 17:50:31.518819: I tensorflow/core/profiler/rpc/client/capture_profile.cc:198] Profiler delay_ms was 0,start_timestamp_ns set to 1612288231518793164 [2021-02-02T17:50:31.518793164+00:00]
Starting to trace for 20000 ms. Remaining attempt(s): 0
2021-02-02 17:50:31.518889: I tensorflow/core/profiler/rpc/client/remote_profiler_session_manager.cc:75] Deadline set to 2021-02-02T17:50:44.890124419+00:00 because max_session_duration_ms was 60000 and session_creation_timestamp_ns was 1612288184890124419 [2021-02-02T17:49:44.890124419+00:00]
2021-02-02 17:50:31.519021: I tensorflow/core/profiler/rpc/client/profiler_client.cc:113] Asynchronous gRPC Profile() to localhost:6009
2021-02-02 17:50:31.519124: I tensorflow/core/profiler/rpc/client/remote_profiler_session_manager.cc:96] Issued Profile gRPC to 1 clients
2021-02-02 17:50:31.519147: I tensorflow/core/profiler/rpc/client/profiler_client.cc:131] Waiting for completion.
2021-02-02 17:50:31.520067: I tensorflow/core/profiler/lib/profiler_session.cc:136] Profiler session initializing.
2021-02-02 17:50:31.520136: W tensorflow/core/profiler/lib/profiler_session.cc:144] Profiling is late (2021-02-02T17:50:31.520095781+00:00) for the scheduled start (2021-02-02T17:50:31.518793164+00:00) and will start immediately.
2021-02-02 17:50:31.520152: I tensorflow/core/profiler/lib/profiler_session.cc:155] Profiler session started.
2021-02-02 17:50:44.891412: W tensorflow/core/profiler/rpc/client/profiler_client.cc:152] Deadline exceeded: Deadline Exceeded
2021-02-02 17:50:44.891501: W tensorflow/core/profiler/rpc/client/capture_profile.cc:133] No trace event is collected from localhost:6009
2021-02-02 17:50:44.891526: W tensorflow/core/profiler/rpc/client/capture_profile.cc:145] localhost:6009 returned Deadline exceeded: Deadline Exceeded
No trace event is collected after 3 attempt(s). Perhaps,you want to try again (with more attempts?).
Tip: increase number of attempts with --num_tracing_attempts.
2021-02-02 17:50:44.891848: I tensorflow/core/profiler/lib/profiler_session.cc:172] Profiler session tear down.
Traceback (most recent call last):
  File "keras_singleworker_2.py",line 37,in <module>
2021-02-02 17:50:44.893228: I tensorflow/core/profiler/internal/gpu/cupti_tracer.cc:1487] CUPTI activity buffer flushed
    tf.profiler.experimental.client.trace('grpc://localhost:6009','./logs/tbc_log',20000)
  File "/fserver/jonathanb/miniconda3/envs/tf2.4/lib/python3.8/site-packages/tensorflow/python/profiler/profiler_client.py",line 131,in trace
    _pywrap_profiler.trace(
tensorflow.python.framework.errors_impl.UnavailableError: No trace event was collected because there were no responses from clients or the responses did not have trace data.

理论上 emails = [get_user(uuid).email for uuid in user_uuids] 可以返回 get_user 的地方，但在这个用例中，我知道它不能（如果有异常，我也可以）。这将必须成为：

None

在 TypeScript 中，有一个 non-null assertion operator 可以让您只添加一个 emails = [] for uuid in user_uuids: user = get_user(uuid) assert user is not None emails.append(user.email) （如 !）。

有没有更好或更优雅的方法来处理这个问题？

解决方法

没有理由不能在条件中使用相同的调用，所以

emails = [get_user(uuid).email for uuid in user_uuids if get_user(uuid)]

会起作用

,

Python 和其他一些语言具有短路功能，因此以下语句完全正确

TestArr = [None,None,None]
ArrTest = [x.testFunc() for x in TestArr if x != None]
print(ArrTest)

并将返回一个空白列表。

虽然我不熟悉 strict_optional。

,

@labroid 有一个很好的答案。一个评论提到调用 get_user 两次并不理想，所以我将在 labroid 的回答基础上创建一个只调用 get_user 一次的语句：

users = [
  {"uuid":"abc","email":"email"}
]

def get_user(uuid):
  for user in users:
    if user["uuid"] == uuid:
      return user
    return None

user_uuids = ["abc","def"]

emails = [user["email"] for user in [get_user(uuid) for uuid in user_uuids] if user != None]

print(emails)