Mixing
Type annotating for ndb.tasklets
GvRs App Engine ndb Library as well as monocle and - to my understanding - modern Javascript use Generators to make async code look like blocking code.
Things are decorated with @ndb.tasklet. They yield when they want to give back execution to the runloop and when they have their result ready they raise StopIteration(value) (or the alias ndb.Return):
@ndb.tasklet
def get_google_async():
context = ndb.get_context()
result = yield context.urlfetch("http://www.google.com/")
if result.status_code == 200:
raise ndb.Return(result.content)
raise RuntimeError
To use such a Function you get a ndb.Future object back and call the get get_result() Function on that to wait for the result and get it. E.g.:
def get_google():
future = get_google_async()
# do something else in real code here
return future.get_result()
This all works very nice. but how to add type Annotations? The correct types are:
- get_google_async() -> ndb.Future (via yield)
- ndb.tasklet(get_google_async) -> ndb.Future
- ndb.tasklet(get_google_async).get_result() -> str
So far, I came only up with casting the async function.
def get_google():
# type: () -> str
future = get_google_async()
# do something else in real code here
return cast('str', future.get_result())
Unfortunately this is not only about urlfetch but about hundreds of Methods- mainly of ndb.Model.
python google-app-engine mypy
edited Jan 14 at 11:59
Dan Cornilescu
30k113767
asked Jan 2 at 16:43
maxmax
16k84667
add a comment |
GvRs App Engine ndb Library as well as monocle and - to my understanding - modern Javascript use Generators to make async code look like blocking code.
Things are decorated with @ndb.tasklet. They yield when they want to give back execution to the runloop and when they have their result ready they raise StopIteration(value) (or the alias ndb.Return):
@ndb.tasklet
def get_google_async():
context = ndb.get_context()
result = yield context.urlfetch("http://www.google.com/")
if result.status_code == 200:
raise ndb.Return(result.content)
raise RuntimeError
To use such a Function you get a ndb.Future object back and call the get get_result() Function on that to wait for the result and get it. E.g.:
def get_google():
future = get_google_async()
# do something else in real code here
return future.get_result()
This all works very nice. but how to add type Annotations? The correct types are:
- get_google_async() -> ndb.Future (via yield)
- ndb.tasklet(get_google_async) -> ndb.Future
- ndb.tasklet(get_google_async).get_result() -> str
So far, I came only up with casting the async function.
def get_google():
# type: () -> str
future = get_google_async()
# do something else in real code here
return cast('str', future.get_result())
Unfortunately this is not only about urlfetch but about hundreds of Methods- mainly of ndb.Model.
python google-app-engine mypy
edited Jan 14 at 11:59
Dan Cornilescu
30k113767
asked Jan 2 at 16:43
maxmax
16k84667
Aren't the results casted automatically if you work with entities? cloud.google.com/appengine/docs/standard/python/ndb/…
– David
Jan 21 at 0:30
add a comment |
GvRs App Engine ndb Library as well as monocle and - to my understanding - modern Javascript use Generators to make async code look like blocking code.
Things are decorated with @ndb.tasklet. They yield when they want to give back execution to the runloop and when they have their result ready they raise StopIteration(value) (or the alias ndb.Return):
@ndb.tasklet
def get_google_async():
context = ndb.get_context()
result = yield context.urlfetch("http://www.google.com/")
if result.status_code == 200:
raise ndb.Return(result.content)
raise RuntimeError
To use such a Function you get a ndb.Future object back and call the get get_result() Function on that to wait for the result and get it. E.g.:
def get_google():
future = get_google_async()
# do something else in real code here
return future.get_result()
This all works very nice. but how to add type Annotations? The correct types are:
- get_google_async() -> ndb.Future (via yield)
- ndb.tasklet(get_google_async) -> ndb.Future
- ndb.tasklet(get_google_async).get_result() -> str
So far, I came only up with casting the async function.
def get_google():
# type: () -> str
future = get_google_async()
# do something else in real code here
return cast('str', future.get_result())
Unfortunately this is not only about urlfetch but about hundreds of Methods- mainly of ndb.Model.
python google-app-engine mypy
edited Jan 14 at 11:59
Dan Cornilescu
30k113767
asked Jan 2 at 16:43
maxmax
16k84667
GvRs App Engine ndb Library as well as monocle and - to my understanding - modern Javascript use Generators to make async code look like blocking code.
Things are decorated with @ndb.tasklet. They yield when they want to give back execution to the runloop and when they have their result ready they raise StopIteration(value) (or the alias ndb.Return):
@ndb.tasklet
def get_google_async():
context = ndb.get_context()
result = yield context.urlfetch("http://www.google.com/")
if result.status_code == 200:
raise ndb.Return(result.content)
raise RuntimeError
To use such a Function you get a ndb.Future object back and call the get get_result() Function on that to wait for the result and get it. E.g.:
def get_google():
future = get_google_async()
# do something else in real code here
return future.get_result()
This all works very nice. but how to add type Annotations? The correct types are:
- get_google_async() -> ndb.Future (via yield)
- ndb.tasklet(get_google_async) -> ndb.Future
- ndb.tasklet(get_google_async).get_result() -> str
So far, I came only up with casting the async function.
def get_google():
# type: () -> str
future = get_google_async()
# do something else in real code here
return cast('str', future.get_result())
Unfortunately this is not only about urlfetch but about hundreds of Methods- mainly of ndb.Model.
python google-app-engine mypy
python google-app-engine mypy
edited Jan 14 at 11:59
Dan Cornilescu
30k113767
asked Jan 2 at 16:43
maxmax
16k84667
edited Jan 14 at 11:59
Dan Cornilescu
30k113767
asked Jan 2 at 16:43
maxmax
16k84667
edited Jan 14 at 11:59
Dan Cornilescu
30k113767
edited Jan 14 at 11:59
Dan Cornilescu
30k113767
edited Jan 14 at 11:59
Dan Cornilescu
30k113767
30k113767
asked Jan 2 at 16:43
maxmax
16k84667
asked Jan 2 at 16:43
maxmax
16k84667
asked Jan 2 at 16:43
maxmax
16k84667
16k84667
Aren't the results casted automatically if you work with entities? cloud.google.com/appengine/docs/standard/python/ndb/…
– David
Jan 21 at 0:30
add a comment |
Aren't the results casted automatically if you work with entities? cloud.google.com/appengine/docs/standard/python/ndb/…
– David
Jan 21 at 0:30
Aren't the results casted automatically if you work with entities? cloud.google.com/appengine/docs/standard/python/ndb/…
– David
Jan 21 at 0:30
Aren't the results casted automatically if you work with entities? cloud.google.com/appengine/docs/standard/python/ndb/…
– David
Jan 21 at 0:30
add a comment |
1 Answer
1
active
oldest
votes
get_google_async itself is a generator function, so type hints can be () -> Generator[ndb.Future, None, None], I think.
As for get_google, if you don't want to cast, type checking may work.
like
def get_google():
# type: () -> Optional[str]
future = get_google_async()
# do something else in real code here
res = future.get_result()
if isinstance(res, str):
return res
# somehow convert res to str, or
return None
answered Jan 21 at 5:29
takataka
1,0975
so whenever I writefuture.get_result()I have to do some kind of type inference magic? I can't teach mypy & co whatfuture.get_result()will returnOptional[str]? :-(
– max
Jan 21 at 8:23
ndb.Futureitself not always return Optional[str], so it is natural to define type hint in each function, maybe...? Like the case you mentionedndb.Model. count_async().get_result() returns int, not str, for example.
– taka
Jan 21 at 9:09
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f54010046%2ftype-annotating-for-ndb-tasklets%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
get_google_async itself is a generator function, so type hints can be () -> Generator[ndb.Future, None, None], I think.
As for get_google, if you don't want to cast, type checking may work.
like
def get_google():
# type: () -> Optional[str]
future = get_google_async()
# do something else in real code here
res = future.get_result()
if isinstance(res, str):
return res
# somehow convert res to str, or
return None
answered Jan 21 at 5:29
takataka
1,0975
so whenever I writefuture.get_result()I have to do some kind of type inference magic? I can't teach mypy & co whatfuture.get_result()will returnOptional[str]? :-(
– max
Jan 21 at 8:23
ndb.Futureitself not always return Optional[str], so it is natural to define type hint in each function, maybe...? Like the case you mentionedndb.Model. count_async().get_result() returns int, not str, for example.
– taka
Jan 21 at 9:09
add a comment |
get_google_async itself is a generator function, so type hints can be () -> Generator[ndb.Future, None, None], I think.
As for get_google, if you don't want to cast, type checking may work.
like
def get_google():
# type: () -> Optional[str]
future = get_google_async()
# do something else in real code here
res = future.get_result()
if isinstance(res, str):
return res
# somehow convert res to str, or
return None
answered Jan 21 at 5:29
takataka
1,0975
so whenever I writefuture.get_result()I have to do some kind of type inference magic? I can't teach mypy & co whatfuture.get_result()will returnOptional[str]? :-(
– max
Jan 21 at 8:23
ndb.Futureitself not always return Optional[str], so it is natural to define type hint in each function, maybe...? Like the case you mentionedndb.Model. count_async().get_result() returns int, not str, for example.
– taka
Jan 21 at 9:09
add a comment |
get_google_async itself is a generator function, so type hints can be () -> Generator[ndb.Future, None, None], I think.
As for get_google, if you don't want to cast, type checking may work.
like
def get_google():
# type: () -> Optional[str]
future = get_google_async()
# do something else in real code here
res = future.get_result()
if isinstance(res, str):
return res
# somehow convert res to str, or
return None
answered Jan 21 at 5:29
takataka
1,0975
get_google_async itself is a generator function, so type hints can be () -> Generator[ndb.Future, None, None], I think.
As for get_google, if you don't want to cast, type checking may work.
like
def get_google():
# type: () -> Optional[str]
future = get_google_async()
# do something else in real code here
res = future.get_result()
if isinstance(res, str):
return res
# somehow convert res to str, or
return None
answered Jan 21 at 5:29
takataka
1,0975
answered Jan 21 at 5:29
takataka
1,0975
answered Jan 21 at 5:29
takataka
1,0975
answered Jan 21 at 5:29
takataka
1,0975
1,0975
so whenever I writefuture.get_result()I have to do some kind of type inference magic? I can't teach mypy & co whatfuture.get_result()will returnOptional[str]? :-(
– max
Jan 21 at 8:23
ndb.Futureitself not always return Optional[str], so it is natural to define type hint in each function, maybe...? Like the case you mentionedndb.Model. count_async().get_result() returns int, not str, for example.
– taka
Jan 21 at 9:09
add a comment |
so whenever I writefuture.get_result()I have to do some kind of type inference magic? I can't teach mypy & co whatfuture.get_result()will returnOptional[str]? :-(
– max
Jan 21 at 8:23
ndb.Futureitself not always return Optional[str], so it is natural to define type hint in each function, maybe...? Like the case you mentionedndb.Model. count_async().get_result() returns int, not str, for example.
– taka
Jan 21 at 9:09
so whenever I write
future.get_result() I have to do some kind of type inference magic? I can't teach mypy & co what future.get_result() will return Optional[str]? :-(– max
Jan 21 at 8:23
so whenever I write
future.get_result() I have to do some kind of type inference magic? I can't teach mypy & co what future.get_result() will return Optional[str]? :-(– max
Jan 21 at 8:23
ndb.Future itself not always return Optional[str], so it is natural to define type hint in each function, maybe...? Like the case you mentioned ndb.Model. count_async().get_result() returns int, not str, for example.– taka
Jan 21 at 9:09
ndb.Future itself not always return Optional[str], so it is natural to define type hint in each function, maybe...? Like the case you mentioned ndb.Model. count_async().get_result() returns int, not str, for example.– taka
Jan 21 at 9:09
add a comment |
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f54010046%2ftype-annotating-for-ndb-tasklets%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Aren't the results casted automatically if you work with entities? cloud.google.com/appengine/docs/standard/python/ndb/…
– David
Jan 21 at 0:30