Develop Reference

create a list from values in array of objects

how i make a list from the values inside urban only for type gasolina?
{ ... "fuelUse" : {
"urban" : [
{
"value" : 6.2,
"unit" : "km/l",
"type" : "alcool"
},
{
"value" : 8.9,
"unit" : "km/l",
"type" : "gasolina"
}
],
},
...."fuelUse" : {
"urban" : [
{
"value" : 7.8,
"unit" : "km/l",
"type" : "alcool"
},
{
"value" : 10.4,
"unit" : "km/l",
"type" : "gasolina"
}
],
}
}
the output like: list = [ 8.9 , 10.4 ]
i tried to iterate in that way, but hav key error: 1
for c in cars:
for a in c['fuelUse']['urban']:
list.append(a[1]['value'])

try
list.append(a['value'])
instead of
list.append(a[1]['value'])
Since a is not a list, it is a single object, there is no need for further indexing.
If you would like the value of the second element, which type is gasolina, from each urban, you should loop through them, not the object's inside.
for c in cars:
for a in c['fuelUse']['urban']:
if a['type'] == 'gasolina':
list.append(a['value'])

I am not quite sure as you did not provide the entire data structure but according to your try it could be like this:
output = [x.get("value") for car in cars for x in car.get("fuelUse").get("urban") if x.get("type") == "gasolina"]

Extracting and updating a dictionary from array of dictinaries in MongoDB

I have a structure like this:
{
"id" : 1,
"user" : "somebody",
"players" : [
{
"name" : "lala",
"surname" : "baba",
"player_place" : "1",
"start_num" : "123",
"results" : {
"1" : { ... }
"2" : { ... },
...
}
},
...
]
}
I am pretty new to MongoDB and I just cannot figure out how to extract results for a specific user (in this case "somebody", but there are many other users and each has an array of players and each player has many results) for a specific player with start_num.
I am using pymongo and this is the code I came up with:
record = collection.find(
{'user' : name}, {'players' : {'$elemMatch' : {'start_num' : start_num}}, '_id' : False}
)
This extracts players with specific player for a given user. That is good, but now I need to get specific result from results, something like this:
{ 'results' : { '2' : { ... } } }.
I tried:
record = collection.find(
{'user' : name}, {'players' : {'$elemMatch' : {'start_num' : start_num}}, 'results' : result_num, '_id' : False}
)
but that, of course, doesn't work. I could just turn that to list in Python and extract what I need, but I would like to do that with query in Mongo.
Also, what would I need to do to replace specific result in results for specific player for specific user? Let's say I have a new result with key 2 and I want to replace existing result that has key 2. Can I do it with same query as for find() (just replacing method find with method replace or find_and_replace)?

You can replace a specific result and the syntax for that should be something like this,
assuming you want to replace the result with key 1,
collection.updateOne({
"user": name,
"players.start_num": start_num
},
{ $set: { "players.$.results.1" : new_result }})

Correctly referencing a JSON in Python. Strings versus Integers and Nested items

Sample JSON file below
{
"destination_addresses" : [ "New York, NY, USA" ],
"origin_addresses" : [ "Washington, DC, USA" ],
"rows" : [
{
"elements" : [
{
"distance" : {
"text" : "225 mi",
"value" : 361715
},
"duration" : {
"text" : "3 hours 49 mins",
"value" : 13725
},
"status" : "OK"
}
]
}
],
"status" : "OK"
}
I'm looking to reference the text value for distance and duration. I've done research but i'm still not sure what i'm doing wrong...
I have a work around using several lines of code, but i'm looking for a clean one line solution..
thanks for your help!

If you're using the regular JSON module:
import json
And you're opening your JSON like this:
json_data = open("my_json.json").read()
data = json.loads(json_data)
# Equivalent to:
data = json.load(open("my_json.json"))
# Notice json.load vs. json.loads
Then this should do what you want:
distance_text, duration_text = [data['rows'][0]['elements'][0][key]['text'] for key in ['distance', 'duration']]
Hope this is what you wanted!

How to Query this in MongoDB?

My items store in MongoDB like this :
{"ProductName":"XXXX",
"Catalogs" : [
{
"50008064" : "Apple"
},
{
"50010566" : "Box"
},
{
"50016422" : "Water"
}
]}
Now I want query all the items belong to Catalog:50008064,how to?
(the catalog id "50008064" , catalog name "Apple")

You cannot query this in an efficient manner and performance will decrease as your data grows. As such I would consider it a schema bug and you should refactor/migrate to the following model which does allow for indexing :
{"ProductName":"XXXX",
"Catalogs" : [
{
id : "50008064",
value : "Apple"
},
{
id : "50010566",
value : "Box"
},
{
id : "50016422",
value : "Water"
}
]}
And then index :
ensureIndex({'Catalogs.id':1})
Again, I strongly suggest you change your schema as this is a potential performance bottleneck you cannot fix any other way.

This should probably work according to the entry here, although this won't be very fast, as stated in in the link.
db.products.find({ "Catalogs.50008064" : { $exists: true } } )

Pythonic way of filtering by descendant element in a dictionary

If I have some json data represented in a dictionary type, what's the pythonic way of finding all 'type' nodes that match a particular value from the 'results' list of items?
"results" : [
{
"address_components" : [
... child elements ...
],
"verified" : "some data here",
"geometry" : {
... child elements ...
},
"types" : [ "type_one" ]
},
{
"address_components" : [
... child elements ...
],
"verified" : "some data here",
"geometry" : {
... child elements ...
},
"types" : [ "type_two" ] // filter all items that match this item's value
},
... more elements ...
]

You can use a list comprehension:
foundItems = [elem for elem in results if 'type_two' in elem['types']]
Of course you'll probably use a variable instead of hard-coding 'type_two' like that.
This will allow other values in the types list alongside the one you are looking for. You can use if elem['types'] == ['type_two'] instead to look for that specific value only.

def search_type(results, search_type):
matching_results = []
for result in results:
if search_type in result["types"]:
matching_results.append(result)
return matching_results