Manipulating and generating YAML file

Anvil Q&A
1

What I’m trying to do:
I have a Jupyter Notebook that I am using to load in an Excel file, then use that file to manipulate a given YAML. In this original notebook, I have heavily relied on using the ruamel package for accessing and manipulating specific elements of that YAML file. As you can imagine, passing a datatype whose structure is of key importance as a media object and then using the get_bytes() mehod on it makes me very wary on the integrity of the data as it passes to and from the server. Below is the snippet of the function I use (after modifying it for Anvil purposes) to manipulate a given YAML (I have only included specific snippets as the code is pretty long):

import anvil.media
from datetime import datetime

@anvil.server.callable

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

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)
    return result

unq_act_patt =  unique_lists(unq_act_deser)
# defining function that finds source pattern
def subtract_30(number):
    while number >= 30:
        number -= 30
    return number


#here I am creating and new YAML to add to using safe_load()


# Create a new YAML object
yaml = ruamel.yaml.YAML()
yaml.preserve_quotes = True  # added in ruamel.yaml
yaml.explicit_start = True   # control also available in PyYAML
yaml.explicit_end = True     # control also available in PyYAML

# Open the YAML file in read-write mode
# Load the YAML documents using the ruamel.yaml.safe_load() method
data = list(yaml.load_all(yml_file))
# Get the third document
doc3 = data[2]

#here the code is looking at specific elements in the YAML and updating it

#Once the code has run and manipulate the different data elements, I am trying to write it back to the YAML
# Seek to the beginning of the file
#file.get_bytes().seek(0)
# Overwrite the file with the updated documents
yaml.dump_all(data, file.get_bytes())
file.write("...\n")
# Close the file
#file.truncate()
#return the file
return file

anvil.server.wait_forever()

What I’ve tried and what’s not working:
Please see my cloned app which has given me the following error:

YAMLStreamError: stream argument needs to have a write() method

  • at C:/Users/hossa/anaconda3/lib/site-packages/ruamel/yaml/emitter.py:227
  • called from C:/Users/hossa/anaconda3/lib/site-packages/ruamel/yaml/main.py:644
  • called from C:/Users/hossa/anaconda3/lib/site-packages/ruamel/yaml/main.py:906
  • called from C:/Users/hossa/anaconda3/lib/site-packages/ruamel/yaml/main.py:913
  • called from C:/Users/hossa/anaconda3/lib/site-packages/ruamel/yaml/main.py:583
  • called from C:/Users/hossa/AppData/Local/Temp/ipykernel_7788/3012870045.py:236
  • called from Form1, line 24

I am sure there is something I am doing wrong or other approaches to reach my objective in a more sensible manner. I look for your experience and wisdom. Thanks!
Code Sample:

# this is a formatted code snippet.
# paste your code between ```

Clone link:
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2

In addition to getting the bytes from the media object, you can write it to a temporary file and then use that file. That might make your YAML library happier: Anvil Docs | Files on Disk

1 Like
3

Thank you,
Would there be any issues running my entire code on the client side to avoid all of these issues?

4

You cannot use custom Python packages in the client.