Merge two arrays with condition on key values in python

Question

I am new to python. I was just trying to do some things to get to know python.

What I am now trying to do is merge two arrays of same size. The condition is that if key is a specific value(nk in my case) then value should be appended to the previous key or current key.

below is the code I wrote to do it and its working. I'm sure that I have written a very bad code(beginner :) )

Below code has two arrays. keys and values. What I am trying to do is, if the value in key is nk then that particular element in values array is appended to a list with the key previously obtained.

import json


keys = ["one", "nk", "nk", "two", "nk", "three", "nk", "four", "nk"]
values = ["quick", "brown", "fox", "jumps", "on", "lazy", "dog", "asfdsagfds", "sdfgre"]
mydict = []
key = "head"
val = []

for i in range(0, len(keys)):
    if(keys[i] != "nk") :
        mydict.append({key:val})
        key = ""
        val = []
        key = keys[i]
        val.append(values[i])
    else :
        val.append(values[i])

    if(i == len(keys)-1) :
        mydict.append({key:val})

print(json.dumps(mydict, indent=4))

Output :

[
    {
        "head": []
    },
    {
        "one": [
            "quick",
            "brown",
            "fox"
        ]
    },
    {
        "two": [
            "jumps",
            "on"
        ]
    },
    {
        "three": [
            "lazy",
            "dog"
        ]
    },
    {
        "four": [
            "asfdsagfds",
            "sdfgre"
        ]
    }
]

Now the question is is there any easy way of doing this using any python inbuilt functions?

reason for -1 will help me :)

Vinay
– Vinay

2020-01-21 08:17:53 +00:00
Commented Jan 21, 2020 at 8:17 — Vinay
– Vinay, Commented Jan 21, 2020 at 8:17

Hrabal · Accepted Answer · 2020-01-21 07:48:40Z

2

In Python you can use the zip function to iterate over two lists at the same time, and you can :

keys = ["one", "nk", "nk", "two", "nk", "three", "nk", "four", "nk"]
values = ["quick", "brown", "fox", "jumps", "on", "lazy", "dog", "asfdsagfds", "sdfgre"]
container = []
my_dict = []
for k, v in zip(keys, values):
    if k != "nk":
        container = []
        my_dict.append({k: container})
    container.append(v)

Generally speaking, using indexes to iterate over lists is considered "un-Pythonic".

answered Jan 21, 2020 at 7:48

Hrabal

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1 Comment

Vinay Over a year ago

Generally speaking, using indexes to iterate over lists is considered "un-Pythonic". Thanks I will consider it :)

Daniel Hepper · Accepted Answer · 2020-01-21 07:35:20Z

Your code is not bad at all. There are no builtin functions solving this particular problem, but you can use zip() to iterate over two lists in parallel. Using zip() combined with the fact that dicts contain references to objects, not copies, allows you to write the code without keeping track of array indices:

keys = ["one", "nk", "nk", "two", "nk", "three", "nk", "four", "nk"]
values = ["quick", "brown", "fox", "jumps", "on", "lazy", "dog", "asfdsagfds", "sdfgre"]
key = "head"
acc = {key: []}
mydict = []

for new_key, value in zip(keys, values):

    if(new_key != "nk") :
        acc = {new_key: []}
        mydict.append(acc)
        key = new_key

    acc[key].append(value)

print(json.dumps(mydict, indent=4))

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