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Is it recommended to use `conditional` inside a `@dynamic` step or should normal python control flow...
# flytekit
e
Is it recommended to use 
conditional
inside a 
@dynamic
step or should normal python control flow work there? We're seeing a number of issues w/ failing to bind variables in a dynamic workflow using normal `if`/`else` blocks
t
Tasks within a dynamic workflow return Promise objects. I think conditional is a better choice. @glamorous-carpet-83516, is 
conditional
supported within dynamic workflows?
g
Yes, it should work
e
Thanks, I'll give that a try!
Something feels strange here...I'm getting the following error w/ the below construct in a 
@dynamic
step (
regress
is a boolean)
Copy code
Logical (and/or/is/not) operations are not supported. Expressions Comparison (<,<=,>,>=,==,!=) or Conjunction (&/|) are supported.Received an evaluated expression with val False in train_estimator.if_
Copy code
flytekit.conditional("train_estimator")
        .if_(regress)
        .then(
            estimator.train_regressor()
         )
        .else_()
        .then(
          estimator.train_classifier()
        )
Seems odd that I can't directly pass a boolean value into 
flytekit.conditional
? (I also tried 
regress == True
as well and that resulted in the same error)
I guess I could push all of this into the task, but then that unfortunately forces us to create a second task for training the estimator vs re-using an existing task
đź‘€ 1
g
Below is the workflow I ran in flyte cluster, it works for me. However, it doesn’t work in local execution now.
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from flytekit import workflow, task, dynamic, conditional


@task
def t1() -> bool:
    return True


@task
def t2() -> bool:
    return False


@dynamic
def d1() -> bool:
    a = t1()
    return (
        conditional("train_estimator")
        .if_(a==True)
        .then(t2())
        .else_()
        .then(t2()))


@workflow
def wf() -> bool:
    return d1()


if __name__ == "__main__":
    print(wf())
e
@glamorous-carpet-83516 does this work if 
a
is an arg to 
d1
vs the result of a task?
g
btw, should use 
regress == True
instead of 
regress
. Otherwise, it will fail
does this work if 
a
is an arg to 
d1
vs the result of a task?
let me try it.
thx 1
it doesn’t work because the type of 
a
is bool instead of promise.
tl;dr 
a
in the if statement must be a promise
e
Hm...ok. Is there a way to do something like 
Promise.of(my_literal)
(kind of abusing JavaScript notation here but you get the point)?
Or maybe another way, is there a reason preventing this from working w/ both promises and literals?
g
Hm...ok. Is there a way to do something like 
Promise.of(my_literal)
(kind of abusing JavaScript notation here but you get the point)?
we don’t have that now, but you could add a task to convert it to a promise in @dynamic
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@task
def convert_to_promise(a: bool) -> bool:
    return a
Or maybe another way, is there a reason preventing this from working w/ both promises and literals
I think we can support pure python type in 
_if
as well. we can try to update it in the next release. For now, to work around this issue, just create a @task to convert it to a promise, sorry.
cc @thankful-minister-83577 @high-accountant-32689 do we have another way to handle 
bool
or 
int
in 
_if
in 
condition
? currently, we can only use promise in condition.
e
Thanks @glamorous-carpet-83516. I'd be happy to contribute this too if there are other milestones you guys are working towards for the next release
g
yeah, I just created an issue for it, feel free to create a pr, thanks.
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