How to optimize python recursion

Question

I have the following code, which must convert this tuple

(
    'person.firstname',
    'person.patronymic',
    'person.documents.type',
    'person.documents.number',
    'person.employee_set.unit.short_name',
    'person.employee_set.group_set.name',
    'person.employee_set.group_set.period.code',
    'unit.short_name',
)

to dictionary like this

    {
    "person": {
        "patronymic": {}, 
        "documents": {
            "type": {}, 
            "number": {}
        }, 
        "employee_set": {
            "unit": {
                "short_name": {}
            }, 
            "group_set": {
                "name": {}, 
                "period": {
                    "code": {}
                }
            }
        }, 
        "firstname": {}
    }, 
    "unit": {
        "short_name": {}
    }
}

code:

def to_dict(items):
    di = {}
    for item in items:
        parse(di, item)
    return di


def parse(di, item): 
    sep = item.find('.')
    if sep != -1:
        key = item[:sep]
        if not key in di.keys():
            di[key] = {}
        return parse(di[key], item[sep + 1:])
    elif len(item) > 0:
        di[item] = {}
        return di

It is possible to optimize this code without recursion? As I understand it there tail recursion, but I do not understand how to transform it in a loop

you may look at this post - stackoverflow.com/a/33327123/5352399 — Wasi Ahmad
– Wasi Ahmad, Commented Dec 7, 2016 at 0:33

martin.macko.47 · Accepted Answer · 2016-12-07 00:41:16Z

2

I rewrote the function without recursion.

def to_dict(items):
    res = {}
    for item in items:
        parts = item.split('.')
        dest = res
        for part in parts:
            if not part in dest:
                dest[part] = {}
            dest = dest[part]
    return res

to_dict([
    'person.firstname',
    'person.patronymic',
    'person.documents.type',
    'person.documents.number',
    'person.employee_set.unit.short_name',
    'person.employee_set.group_set.name',
    'person.employee_set.group_set.period.code',
    'unit.short_name',
])

The alorithm: I split every path into its parts and then build subdicts in a loop keeping a reference dest to the part of dictionary I'm currently in.

answered Dec 7, 2016 at 0:41

martin.macko.47

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1 Comment

DexFuris Over a year ago

Thanks. I learn programming during the week, and you have helped me greatly.

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