Passing Server Callable Function Returns to other Server functions

Anvil Q&A
1

I am relatively new to Anvil and am still trying to wrap my head around building applications
that use a server (I usually just run my code in an IDE), so I appreciate the patience and help.

What I’m trying to do:
I want to use the client as a bridge to pass data between two server-callable functions. I have two server functions that I am calling from the client side:

  1. ‘tod_preprocess’: This function returns three variables (tod_df, dp_plans_all_ser, unq_act_ser) as shown in the cloned app. I am returning these variables since some of them will be needed for the second server-callable function, ‘yaml_process’, to be executed.
  2. ‘yaml_process’

As you can see from the cloned app, I am correctly assigning the returns to variables. However, I get a NameError:

NameError: name 'unq_act_ser' is not defined

Here is applicable part of my client-side code:

def file_loader_1_change(self, file, **event_args):
“”“This method is called when a new file is loaded into this FileLoader”“”
tod_df, dp_plans_all_ser, unq_act_ser = anvil.server.call(‘tod_preprocess’, file)
self.tod_table.content = tod_df # displaying the final dataframe

def file_loader_2_change(self, file, **event_args):
“”“This method is called when a new file is loaded into this FileLoader”“”
yaml_processed = anvil.server.call(‘yaml_process’, file, unq_act_ser)
anvil.media.download(yaml_processed)

And this is a portion of the server-function that I have an issue with (it is a couple hundred lines so I am only including the applicable portion), yaml_process:

import anvil.media

@anvil.server.callable

def yaml_process(file, unq_act_ser):
unq_act_deser = json.loads(unq_act_ser)
#importing the yaml
yml_file = file
import ruamel.yaml

Blockquote

def unique_lists(lst_of_lsts): #defining unique lists for unq_act so that we iterate over them and create plans.
unique = set()
result =
for lst in lst_of_lsts:
if tuple(lst) not in unique:
unique.add(tuple(lst))
result.append(lst)

Clone link:
share a copy of your app

2

You’re running into variable scope issues. A variable defined in one function is not automatically available in another function. So the unq_act_ser variable defined in file_loader_1_change is not available in file_loader_2_change.

To pass values between functions in a form like that, set the variable on the form itself using self., e.g.:

tod_df, dp_plans_all_ser, self.unq_act_ser = anvil.server.call(‘tod_preprocess’, file)

and

yaml_processed = anvil.server.call(‘yaml_process’, file, self.unq_act_ser)

3

Thank you very much, that makes much more sense. However, I do have the following questions:

  1. Now that I understand what I need to do on the client-side, does anything else need to be done on the server-side? That is, I now make a call from the client with ‘self.unq_act_ser’ as an argument. However, on the server-side does the server-callable function ‘yaml_process’ need to be changed to also have an argument of ‘self.unq_act_ser’?

  2. I tried following your suggestion and have not changed anything outside of it. However, when running the code, I get the following error:

TypeError: 'StreamingMedia' object is not subscriptable
at C:/Users/hossa/AppData/Local/Temp/ipykernel_2488/1857508715.py:38
called from Form1, line 24

Thanks a lot for the help and your patience.

4

Your server function does not need to change.

As far as the error you’re getting, which line is line 24 in Form1?

5

This one:

yaml_processed = anvil.server.call('yaml_process', file, self.unq_act_ser)
6

That one I’m not sure about. The error message sounds like at some point you’re trying to index into a media object. You’re not doing that on line 24 in the form, and the error message is pointing to a temporary file on your PC. So your server functions must be in an uplink, right? You might have gotten an error message in the uplink’s console that would give a better idea of where in the server function things went wrong.

7

Hi,
Yes, you are right. I am not indexing on Line 24 in the form, rather, I am using the Server function ‘yaml_process’ to read the yaml file. On line 38 of the Server function, I am trying to index the yaml file which works fine when I am executing this locally in my Jupyter notebook. However, now it seems that the file is a ‘streamingmedia’ type, there are limitations on how to index it. I think this may belong on a different thread to avoid confusion. Let me know if you concur and I will start a new thread to keep things clear.

8

I agree, a different topic makes sense. The environment is different between the Anvil server an Jupyter notebooks, so different techniques are often needed in each.

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