Creating runtime variable in python to fetch data from dictionary object

Question

I have created dictionary object my parsing a json file in python....lets assume the data is as follows

    plants = {}  

# Add three key-value tuples to the dictionary.
plants["radish"] = {"color":"red", "length":4} 
plants["apple"] = {"smell":"sweet", "season":"winter"}
plants["carrot"] = {"use":"medicine", "juice":"sour"}

This could be a very long dictionary object

But at runtime, I need only few values to be stored in a commaa delimited csv file.....The list of properties desired is in a file.... e.g

radish.color
carrot.juice

So, how would I create in python an app, where I can created dynamic variables such as below to get data of the json object & create a csv file....

at runtime i need variable

plants[radish][color]
plants[carrot][juice]

Thank you to all who help

Sanjay

How do you create variable DYNAMICALLY at runtime in pythin code .....if I have 100 such combinations of radish.color or carrot.juice or mango.season in a file ....How would I write code to fetch the above values at runtime from the dictionary object, by reading the strings radish.color , carrot.juice , mango.season from an external file... As asked by depperm...I havent tried it, as am not aware how to solve it — sshroff
– sshroff, Commented Aug 11, 2016 at 17:30
The list of variable I need to fetch from dictionary object vary.....some are 1 level deep, or 2 levels, 3 or further.....such as radish radish.color watermellon.season.fertilizer I need to fetch values of above set of variables & export to a csv file — sshroff
– sshroff, Commented Aug 11, 2016 at 17:36

Parfait · Accepted Answer · 2016-08-11 20:34:34Z

1

Consider parsing the text file line by line to retrieve file contents. In the read, split the line by period which denotes the keys of dictionaries. From there, use such a list of keys to retrieve dictionary values. Then, iteratively output values to csv, conditioned by number of items:

Txt file

radish.color 
carrot.juice

Python code

import csv

plants = {}  
plants["radish"] = {"color":"red", "length":4} 
plants["apple"] = {"smell":"sweet", "season":"winter"}
plants["carrot"] = {"use":"medicine", "juice":"sour"}

data = []
with open("Input.txt", "r") as f:
    for line in f:
        data.append(line.replace("\n", "").strip().split("."))

with open("Output.csv", "w") as w:
    writer = csv.writer(w,  lineterminator = '\n')

    for item in data:            
        if len(item) == 2:   # ONE-NEST DEEP
            writer.writerow([item[0], item[1], plants[item[0]][item[1]]])
        if len(item) == 3:   # SECOND NEST DEEP
            writer.writerow([item[0], item[1], item[2], plants[item[0]][item[1]][item[2]]])

Output csv

radish,color,red
carrot,juice,sour

(Note: the deeper the nest, the more columns will output conflicting with key/value pairs across columns -maybe output different structured csv files like one-level files/second-level files)

answered Aug 11, 2016 at 20:34

Parfait

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4 Comments

sshroff Over a year ago

Parfait: You have a very good solution..I was only hoping if the multiple if clauses could be avoided & soultion automated as we know the len(items) One thing I have been trying is to use eval( plants[item[0]][item[1]]]) function and keep appending to the key as follows

sshroff Over a year ago

#each_property is list of keys in file ( . delimited ) #each_property = radish.color #each_property = watermellon.season.fertilizer

sshroff Over a year ago

for sdr in data: csvString='' for each_property in the_properties_list: thekeys = each_property.split(".") i =0 for thekey in thekeys: if (i==0): fullkey="sdr[" + "\"" + thekey + "\"" + "]" else: fullkey=fullkey + "[" + "\"" + thekey + "\"" + "]" i=i+1 try: csvString=csvString + "\t" + eval( "'" + fullkey + "'") except Error: csvString=csvString + "\t" + ''

Parfait Over a year ago

Anticipating different levels of nested dictionaries for any possibility might involve nested loops or list comprehensions/generators or even a recursive function. Consider anticipating length as this simpler solution does or go another route.

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