Is there a python function like Clojure's get-in?

Question

Is there something equivalent to Clojure's get-in function in Python? It gets the data at the given path in some data structure.

In Clojure it is used like:

(def employee
  {:name "John"
   :details {:email "info@domain.com"
             :phone "555-144-300"}})

(get-in employee [:details :email])  ; => "info@domain.com"

If translated to Python syntax it would be used like:

dictionary = {'a': {'b': 10}}
get_in(dictionary, ['a', 'b'])  # => 10

This function is used to access arbitrary data points in nestled data structures where the paths are not known at compile time, they are dynamic. More usage examples of get-in can be found on clojuredocs.

maybe [this](https://codereview.stackexchange.com/questions/156144/get-value-from-dictionary-given-a-list-of-nested-keys) can help. — Plopp, Aug 20 '18 at 11:24
@Rovanion then you may want to clarify your question and example code - in your example the path is hardcoded. — bruno desthuilliers, Aug 20 '18 at 12:07
@brunodesthuilliers Added a short clearification and a link with further usage and documentation. — Rovanion, Aug 20 '18 at 12:19
[This](https://stackoverflow.com/q/19189274/1435475) is a similar question, but the solution has the added benefit of being able to write the found object. — guidot, Aug 20 '18 at 12:41

FHTMitchell · Answer 1 · 2018-08-20T11:26:42.257

2

No, but you can certainly make one

def get_in(d, keys):
   if not keys:
       return d
   return get_in(d[keys[0]], keys[1:])

edited Aug 20 '18 at 11:26

answered Aug 20 '18 at 11:20

FHTMitchell

11,793
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[A bit more complete version](https://utgwkk.hateblo.jp/entry/2016/11/14/144209) outside Stack Overflow... (blog is Japanese, but code is code) – Amadan Aug 20 '18 at 11:23
@Amadan, Good one. – sat Aug 20 '18 at 11:25
This will throw an exception if a key is missing - which is different from the Clojure behaviour. – Aleph Aleph Aug 20 '18 at 11:28
2

@AlephAleph I saw your answer, didn't have to point it out here too... And in python we're a bit more happy to handle errors than in a functional language like closure. I'd rather get a `KeyError` than `None` which could be either a result or a fail. Let the user decide how they want to handle a fail. – FHTMitchell Aug 20 '18 at 11:30

score 1 · Accepted Answer · answered Aug 20 '18 at 11:26

You can write:

dictionary.get('details', {}).get('email')

This will safely get the value you need or None, without throwing an exception - just like Clojure's get-in does.

If you need a dedicated function for that, you can write:

def get_in(d, keys):
    if not keys:
        return d
    elif len(keys) == 1:
        return d.get(keys[0])
    else:
        return get_in(d.get(keys[0], {}), keys[1:])

Sushant · Answer 3 · 2018-08-20T12:07:35.750

0

A simple for loop should solve your problem -

x = {'a':{'b':{'c': 1}}}

def get_element(elements, dictionary):
    for i in elements:
        try:
            dictionary = dictionary[i]
        except KeyError:
            return False
    return dictionary

print(get_element(['a', 'b', 'c'], x))
# 1
print(get_element(['a', 'z', 'c'], x))
# False

edited Aug 20 '18 at 12:07

answered Aug 20 '18 at 11:17

Sushant

3,499
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Is there a python function like Clojure's get-in?

3 Answers3