python how to search in multidimensional array / list

Question

I cannot figure out how to search in the follow list/array (stored in self._map_commodities) and the data is obtained from JSON.

The problem: I want to locate "wood" in the array and return the "size" value related to it

I have tried to use index(), but I cannot get it to work. T

class MyClass1(object):

    def __init__(self):
        self._data = ''
        self.list_commodities = []
        self._map_commodities = []

    def create_commodity_market(self):
        for commodity in self._data['commodities']:
            self.list_commodities.append(commodity['id'])
            self._map_commodities.append(commodity)

    def from_json(self):
        import json
        self._data = json.loads('{"commodities":[{"id":"food","size":"1.0"},{"id":"wood","size":"1.0"},{"id":"ore","size":"1.0"},{"id":"metal","size":"1.0"},{"id":"tools","size":"1.0"}]}')


x = MyClass1()
x.from_json()
x.create_commodity_market()
print(x.list_commodities)
print(x._map_commodities)
####print(x._map_commodities.index("wood")) # I want it to print the size-value of the wood object

Thank you in advance.

['food', 'wood', 'ore', 'metal', 'tools'] [{'id': 'food', 'size': '1.0'}, {'id': 'wood', 'size': '1.0'}, {'id': 'ore', 'size': '1.0'}, {'id': 'metal', 'size': '1.0'}, {'id': 'tools', 'size': '1.0'}] I need a way to search/match id's (food, wood, ore, metal, tools) and return the "size" related to them. I know everyone has size: 1.0 but they could be different. — haakoon
– haakoon, Commented Mar 11, 2015 at 20:44

mobeets · Accepted Answer · 2015-03-11 20:43:20Z

1

Basically what you want is:

print next(y['size'] for y in x._map_commodities if y['id'] == 'wood')

Which will throw an StopIteration exception if none of your items have the id 'wood'.

More generally, add a method like this to MyClass1:

def size_from_id(self, id_name):
    try:
        return next(y['size'] for y in self._map_commodities if y['id'] == id_name)
    except StopIteration:
        return None

Then you can call x.size_from_id('wood').

answered Mar 11, 2015 at 20:43

mobeets

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Comments

Jan Buchar · Accepted Answer · 2015-03-11 20:44:59Z

0

A dictionary is more suitable for what you're trying to do:

class MyClass1(object):

def __init__(self):
    self._data = ''
    self._map_commodities = {}

def create_commodity_market(self):
    for commodity in self._data['commodities']:
        self._map_commodities[commodity['id']] = commodity['size']

def from_json(self):
    import json
    self._data = json.loads('{"commodities":[{"id":"food","size":"1.0"},{"id":"wood","size":"1.0"},{"id":"ore","size":"1.0"},{"id":"metal","size":"1.0"},{"id":"tools","size":"1.0"}]}')


x = MyClass1()
x.from_json()
x.create_commodity_market()
print(x._map_commodities["wood"])

answered Mar 11, 2015 at 20:44

Jan Buchar

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Comments

zyxue · Accepted Answer · 2015-03-11 20:44:36Z

0

You could use pandas to handle the data

import json
import pandas as pd

data = json.loads('{"commodities":[{"id":"food","size":"1.0"},{"id":"wood","size":"1.0"},{"id":"ore","size":"1.0"},{"id":"metal","size":"1.0"},{"id":"tools","size":"1.0"}]}')
df = pd.DataFrame.from_dict(data['commodities'])

# get the size of the row with id = 'wood'
size = df[df['id'] == 'wood']['size']
print size

# you can get the value alone, too
print size.values[0]

answered Mar 11, 2015 at 20:44

zyxue

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Comments

Kasravnd · Accepted Answer · 2015-03-11 20:48:46Z

0

First of all you need to return the specific value on your function :

def from_json(self):
        import json
        self._data = json.loads('{"commodities":[{"id":"food","size":"1.0"},{"id":"wood","size":"1.0"},{"id":"ore","size":"1.0"},{"id":"metal","size":"1.0"},{"id":"tools","size":"1.0"}]}')
        return self._data

Then use indexing to get the related size of a word.for example :

x = MyClass1()
d=x.from_json()
print d['commodities'][1]['size']
u'1.0'

edited Mar 11, 2015 at 20:48

answered Mar 11, 2015 at 20:37

Kasravnd

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1 Comment

user3885927 Over a year ago

"return elf._data" should be "return self._data"

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