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My python function is returning None, even if after declaring return statement. I’m unable to understand where I am legging. Recursion is mandatory

# i want to read 'jsondict' json below store it in cond,field,operator,val variable using recursion(mandatory) but my function returning None, what should i do.

”’ jsondict = { “condition”: “AND”, “rules”: [ { “id”: “price”, “field”: “price”, “type”: “double”, “input”: “number”, “operator”: “less”, “value”: 10.25 }, { “condition”: “OR”, “rules”: [ { “id”: “category”, “field”: “category”, “type”: “integer”, “input”: “select”, “operator”: “equal”, “value”: 2 }, { “id”: “category”, “field”: “category”, “type”: “integer”, “input”: “select”, “operator”: “equal”, “value”: 1 } ] } ] }

    cond = []
    field = []
    operator = []
    val = []
    
    def rules(n):   
        for key, value in n.items():
            #print(key, value)
            if key == 'condition':
              cond.append(value)
                       
            elif key == 'rules':
                #print(key, values)
                for i in value:
                    #print(i)
                    for a, b in i.items():
                        #print(a,b)
                        if a == 'field':
                            field.append(b)
                            #print(b)
                        elif a == 'operator':
                            operator.append(b)
                        elif a == 'value':
                            val.append(b)
                        elif a == 'condition':
                            cond.append(b)
                        elif a == 'rules':
                            for j in b:
                                print(rules(j))
                                return rules(j)   # HERE CALLING FUNTION
    rules(jsondict)    
    
    print(field)      # CHECKING IF VALUES GOING IN VARIABLES
    print(operator)
    print(val)
    print(cond)

”’

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Answer

  1. In the 2nd step of recursion, you apply your rules method to this kind of dicts:

{ “id”: “category”, “field”: “category”, “type”: “integer”,
“input”: “select”, “operator”: “equal”, “value”: 2 }

It does not work because there is no “rules” key.

  1. Moreover, returning the function causes a break of for loop. Call the method without the “return” keyword.

Try something like this:

def rules(n):
  for key, value in n.items():
    if key == 'condition':
      cond.append(value)
    elif key =='field':
      field.append(value)
    elif key == 'operator':
      operator.append(value)
    elif key == 'value':
      val.append(value)
    elif key == 'rules':
      for v in value:
        rules(v)
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