Copy Content From One Yaml To Another Yaml After Comparison Of Keys

I have a use case where I need to pick key:value pairs from a new YAML file. Check whether that key exists in old YAML file and if it does copy the value and set it in new YAML fil

Solution 1:

That is invalid Python, your try doesn't have a matching except. Apart from that it is not necessary to open the second file in the context of the with statement that you use for reading in the "old" file. Therefore start with:

import ruamel.yaml

copyfile('all.isv', '/home/ubuntu/tmp/deploy/all')
withopen("/home/ubuntu/ansible-environments/aws/lp/all", 'r') as f1:
    oldvars = ruamel.yaml.round_trip_load(f1)

You cannot open a YAML file for reading and writing, therefore just read it (and opening for reading and writing of a file is done with 'r+' not with 'rw'):

withopen("/home/ubuntu/tmp/deploy/all", 'r') as f2:
    newvars = ruamel.yaml.round_trip_load(f2)

After that continue unindented and update newvars from oldvars if appropriate:

for key in newvars:
    if key in oldvars:
        # this copies the value from the old file if the key exists in there
        value =  oldvars[key] 
    else:
        # ask the user for a new value
        value = raw_input("Enter the value ")
    # update the value in newvars
    newvars[key] = value
# and write the update mapping backwithopen("/home/ubuntu/tmp/deploy/all", 'w') as f2:
     ruamel.yaml.round_trip_dump(newvars, f2)

Combining that and naming your files old.yaml and new.yaml and answering the prompt with 'abcd':

import sys
import ruamel.yaml

withopen('new.yaml') as fp:
    newvars = ruamel.yaml.round_trip_load(fp)
withopen('old.yaml') as fp:
    oldvars = ruamel.yaml.round_trip_load(fp)
for key in newvars:
    if key in oldvars:
        # this copies the value from the old file if the key exists in there
        value =  oldvars[key]
    else:
        # ask the user for a new value
        value = raw_input("Enter the value ")
    # update the value in newvars
    newvars[key] = value
ruamel.yaml.round_trip_dump(newvars, sys.stdout)

gives you:

Enter the value abcd
# Enter the release and build you wish to deploy
release:'4.0'build:'4_0_178'ems_release:'4.0'ems_build:'4_0_999'build_type: test_build
# The name prefix is synonymous with the stack (i.e. pdx02-cloud-prod)
name_prefix: syd01-devops-deepali

# The deployment type is one of: [ test | trial | dev | prod ]
deployment_type: trial
# deployment_url is typically the same value as deployment type unless it is a premium deployment.
# In that case deployment_type issetto prod and deployment_url is either dev, trial or test
deployment_url:'{{ deployment_type }}'some_new_var: abcd

Please note that:

• this only runs on Python 2.7
• for scalars that do not need them quotes are dropped
• I did not try to include the four space indentation of your output past the first line.