Hello everyone I am trying to access a Parameter from within

Question

Hello everyone I am trying to access a Parameter from within a state handler using prefect context get parameters get stakeholderEmail When I run my code I get no errors but it does result in my variable containing the emails to be a nonetype Is my approach the proper method for retrieving a parameter from inside a state handler or is there a better way to do this

Zachary Hughes · Answer

Hi < Kyle Combs> Asking around with the team for best practices will be back with an answer as soon as I have one

Jim Crist-Harif · Answer

Hi < Kyle Combs> can you provide a reproducible example I m unable to reproduce ```import prefect from prefect import task Flow Parameter def handler task old new print prefect context parameters task state handlers= handler def inc x return x + 1 with Flow test state handlers= handler as flow a = Parameter a b = inc a flow run a=1 ```

Jim Crist-Harif · Answer

```$python test py 2020 07 14 22 09 10 INFO prefect FlowRunner | Beginning Flow run for test 2020 07 14 22 09 10 INFO prefect FlowRunner | Starting flow run a 1 2020 07 14 22 09 10 INFO prefect TaskRunner | Task a Starting task run 2020 07 14 22 09 10 INFO prefect TaskRunner | Task a finished task run for task with final state Success 2020 07 14 22 09 10 INFO prefect TaskRunner | Task inc Starting task run a 1 a 1 2020 07 14 22 09 10 INFO prefect TaskRunner | Task inc finished task run for task with final state Success 2020 07 14 22 09 10 INFO prefect FlowRunner | Flow run SUCCESS all reference tasks succeeded a 1 ```

Kyle Combs · Answer

```def jobFailed task old state new state grabbing email parameter emails = prefect context get parameters get stakeholderEmail split print EMAIL emails ``` ```with Flow ComputationWS state handlers= jobFailed as flow stakeholder = Parameter stakeholder default= John Doe stakeholderEmail = Parameter Emails separated by comma space default = ```

Kyle Combs · Answer

``` base $ python prefectComputeWS py 2020 07 15 13 07 06 INFO prefect FlowRunner | Beginning Flow run for ComputationWS 2020 07 15 13 07 06 INFO prefect FlowRunner | Starting flow run 2020 07 15 13 07 06 ERROR prefect FlowRunner | Unexpected error while calling state handlers AttributeError NoneType object has no attribute split ```

Jim Crist-Harif · Answer

Looks like you re indexing with the parameter object `stakeholderEmail` instead you want to index with the string name of the parameter ` Emails separated by comma space `

Jim Crist-Harif · Answer

```def jobFailed task old state new state grabbing email parameter emails = prefect context parameters string name of your parameter split print EMAIL emails ```

Jim Crist-Harif · Answer

Generally you want `Parameter` names to be some short memorable name like ` stakeholder emails ` not a description of their purpose There s nothing wrong with using a longer name of course

Kyle Combs · Answer

Hi I altered my code and changed the string name of the parameter to be stakeholderEmail I tried running my code again and am now getting the following error ```emails = prefect context parameters stakeholderEmail split KeyError parameters 2020 07 15 13 19 15 ERROR prefect ComputationWS | Unexpected error occured in FlowRunner KeyError parameters ```

Kyle Combs · Answer

```with Flow ComputationWS state handlers= jobFailed as flow stakeholderEmail = Parameter stakeholderEmail default = kyle combs email nick he email ```

Jim Crist-Harif · Answer

```import prefect from prefect import task Flow Parameter def handler task old new emails = prefect context parameters stakeholder emails print f Emails are emails task state handlers= handler def echo x return print x with Flow test state handlers= handler as flow stakeholder emails = Parameter stakeholder emails default= <mailto alice google com|alice google com> b = echo stakeholder emails flow run ```

Jim Crist-Harif · Answer

```$ python test py 2020 07 15 13 28 17 INFO prefect FlowRunner | Beginning Flow run for test 2020 07 15 13 28 17 INFO prefect FlowRunner | Starting flow run Emails are 2020 07 15 13 28 17 INFO prefect TaskRunner | Task stakeholder emails Starting task run 2020 07 15 13 28 18 INFO prefect TaskRunner | Task stakeholder emails finished task run for task with final state Success 2020 07 15 13 28 18 INFO prefect TaskRunner | Task echo Starting task run Emails are Emails are 2020 07 15 13 28 18 INFO prefect TaskRunner | Task echo finished task run for task with final state Success 2020 07 15 13 28 18 INFO prefect FlowRunner | Flow run SUCCESS all reference tasks succeeded Emails are ```

Jim Crist-Harif · Answer

Since your parameter was never used in your flow it wasn t actually added to the flow You either need to pass the parameter to a task or use `flow add task parameter ` to add it to your flow manually

Kyle Combs · Answer

Hi sorry but I am still unable to get this to work I end up eventually passing the parameter to a task in my flow Here is the entirety of it ``` State handler to notify is flow has failed def jobFailed task old state new state grabbing email parameter emails = prefect context parameters stakeholder emails print EMAIL emails with Flow ComputationWS state handlers= jobFailed as flow stakeholderEmail = Parameter stakeholder emails default = kyle combs email nick he email rundate = Parameter rundate default = date datadir = Parameter datadir default = xyz ref = Parameter ref default = abc refpb = Parameter refpb default = adx callComp = callComputeService rundate datadir ref refpb checkStat = checkStatus callComp buildResults = createTable checkStat 0 checkStat 1 stakeholderEmail ``` I pass in the stakeholderEmail parameter when I call my createTable function at the bottom of the code block As before I am still getting the following key error ```File prefectComputeWS py line 143 in jobFailed emails = prefect context parameters stakeholder emails File home user anaconda3 lib python3 7 site packages prefect utilities collections py line 79 in getitem return self dict key dict expects string keys KeyError parameters ``` Sorry for the confusion

Jim Crist-Harif · Answer

```import prefect from prefect import Flow task Parameter State handler to notify is flow has failed def jobFailed task old state new state grabbing email parameter emails = prefect context parameters stakeholder emails print EMAIL emails task def callComputeService rundate datadir ref refpb pass task def checkStatus callComp return 0 1 fake data task def createTable checkStat0 checkStat1 stakeholderEmail pass with Flow ComputationWS state handlers= jobFailed as flow stakeholderEmail = Parameter stakeholder emails default = kyle combs email nick he email rundate = Parameter rundate default = date datadir = Parameter datadir default = xyz ref = Parameter ref default = abc refpb = Parameter refpb default = adx callComp = callComputeService rundate datadir ref refpb checkStat = checkStatus callComp buildResults = createTable checkStat 0 checkStat 1 stakeholderEmail flow run ```

Jim Crist-Harif · Answer

```$ python test py 2020 07 15 13 58 10 INFO prefect FlowRunner | Beginning Flow run for ComputationWS 2020 07 15 13 58 10 INFO prefect FlowRunner | Starting flow run EMAIL kyle combs email nick he email 2020 07 15 13 58 10 INFO prefect TaskRunner | Task ref Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task ref finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect TaskRunner | Task rundate Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task rundate finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect TaskRunner | Task datadir Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task datadir finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect TaskRunner | Task refpb Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task refpb finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect TaskRunner | Task stakeholder emails Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task stakeholder emails finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect TaskRunner | Task callComputeService Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task callComputeService finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect TaskRunner | Task checkStatus Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task checkStatus finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect TaskRunner | Task GetItem Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task GetItem finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect TaskRunner | Task GetItem Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task GetItem finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect TaskRunner | Task createTable Starting task run 2020 07 15 13 58 10 INFO prefect TaskRunner | Task createTable finished task run for task with final state Success 2020 07 15 13 58 10 INFO prefect FlowRunner | Flow run SUCCESS all reference tasks succeeded EMAIL kyle combs email nick he email```

Jim Crist-Harif · Answer

What version of prefect are you using

Kyle Combs · Answer

0 11 4

Jim Crist-Harif · Answer

Try upgrading to the most recent release perhaps The latest release is 0 12 4

Kyle Combs · Answer

That was it Thank you for all of your help

Jim Crist-Harif · Answer

No problem glad you got things working