Python Dict Key with Multiple Values

Question

I'm learning about dictionaries, and I know I could do this by creating two more dictionaries, but for brevity's sake, I wanted to make the code a bit more concise than having to create two more dict (granted, in the end, everything I wrote out for this dict would have to be written in the other dicts), so I guess I'm more curious than anything. And I know that I shouldn't be using a for-loop, but I don't know another way, and as far as LPTH sucking, I had to start somewhere.

question 1: How can I get this to cycle through each state/abbrev/city? Would I have to just make multiple dicts, or a series of lists and use those? question2: Why does this code run the for-loop 11 times?

states1 = {
    '1': 'Oregon', 'a': 'OR','population': '1000',
    '2': 'Florida', 'b': 'MI', 'population': '1000',
    '3': 'California', 'c': 'CA', 'population': '1000',
    '4': 'NewYork', 'd': 'NY', 'population': '1000',
    '5': 'Michigan','e': 'MI','population': '1000',
}

for city, pop, in states1.items():
    print "%s has the abbreviation %s and a population of %s" %states1['1'], states1['a'], states1['population'])

mgilson · Accepted Answer · 2016-06-13 22:45:45Z

1

Ideally, you'd have a homgonous datastructure -- e.g. a list of dict¹. Each dict would hold the information about a particular state:

states1 = [
  {'name': 'Oregon', 'abbrev': 'OR', 'population': 1000},
  {'name': 'Florida', 'abbrev': 'FL', 'population': 1000},
  ...,
]

Now your loop looks like this:

for state in states1:
    print print "%s has the abbreviation %s and a population of %s" % (state['name'], states['abbrev'], states['population'])

The benefit here is hopefully clear. For any given state, you retrieve the related information the same way (the state's name is always reachable via the 'name' key).

If you ever need a mapping of state names (e.g. you want to look up a bunch of state's populations by their abbreviation), you can do that pretty easily by creating a dict...

abbrev_to_state = {state['abbrev']: state for state in states1}
florida_data = abbrev_to_state['FL']
new_hampshire_data = abbrev_to_state['NH']
...

^{¹There are other options here too... You could use a custom class, but this also seems like a good candidate for a list of collections.namedtuple assuming you aren't planning on mutating the data.}

answered Jun 13, 2016 at 22:45

mgilson

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1 Comment

Wolverine Over a year ago

That helped a TON mgilbson and I cannot believe I did not think about that, it seems so stupidly simple now!

SirSteel · Accepted Answer · 2016-06-13 22:59:34Z

0

You could make each value be a list.

I do not understand what exactly you want to achieve, but the easy way would be:

states1 = {
1: ["Oregon", "OR", 1000]
2: ["Florida", "FL", 1000]
3: ["Pythonville", "PY", 1000]
4: ["Dictville", "DI", 1000]
}

Another thing you could look up is named tuple, it is one of my favorite data structures for when you want to quickly organize data.

from collections import namedtuple

CityInfo = namedtuple("CityInfo", ["Name", "Abbr", "Pop"])

states1 = {
            1: CityInfo("Oregon", "OR", 1000),
            2: CityInfo("Florida", "FL", 1000),
            3: CityInfo("Pythonville", "PY", 1000),
            4: CityInfo("Dictville", "DI", 1000)
            }

for city in states1.values():
    print("{} has the abbreviation {} and a population of {}".format(city.Name, city.Abbr, city.Pop))

answered Jun 13, 2016 at 22:59

SirSteel

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2 Comments

mgilson Over a year ago

FWIW, a dict with sequential integers as keys seems a bit like a waste of memory. a list is usually better in this case :-)

SirSteel Over a year ago

True, yeah. But I did not want to completely change his code.

Wolverine · Accepted Answer · 2016-06-13 23:03:44Z

When I run it as you recommended me to (below), it spits out

Michigan has the abbreviation MI and a population of 1000
Michigan has the abbreviation MI and a population of 1000
Michigan has the abbreviation MI and a population of 1000

not sure why it's continually doing that, I would have guessed if it was for some reason to choose a totally random state because it's a dictionary that it would change the state each time, with occasional duplicates.

states1 = {
    'state': 'Oregon', 'abbrev': 'OR','population': '10000',
    'state': 'Florida', 'abbrev': 'MI', 'population': '1000',
    'state': 'California', 'abbrev': 'CA', 'population': '1000',
    'state': 'NewYork', 'abbrev': 'NY', 'population': '1000',
    'state': 'Michigan','abbrev': 'MI','population': '1000',
}

for city, pop, in states1.items():
    print "%s has the abbreviation %s and has a population of %s" % (states1['state'], states1['abbrev'], states1['population'])

user4642224 · Accepted Answer · 2016-06-13 23:05:05Z

0

Another example of how you could structure your data depending on your needs.

states1 = {
'Oregon': {'abrv': 'OR','population': '1000'},
'Florida':{ 'abrv': 'MI', 'population': '1000'},
'California':{'abrv': 'CA', 'population': '1000'},
'NewYork':{'abrv': 'NY', 'population': '1000'},
'Michigan':{'abrv': 'MI','population': '1000'}}



for state in states1:
  print "%s has the abbreviation %s and a population of %s" %(state, states1[state]['abrv'], states1[state]['population'])

answered Jun 13, 2016 at 23:05

user4642224

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2 Comments

Wolverine Over a year ago

Thought this looked really perfect in my mind, as did the first suggestion, but both are giving me errors. This one says " File "ex39-test2.py", line 12, in <module> print "%s has the abbreviation %s and has a population of %s" % (state, states1[state]['abbrev'], states1[state]['population']) TypeError: unhashable type: 'dict'"

user4642224 Over a year ago

Not sure why you're getting that error if your're the exact code. Unhashable dict type would raise if I tried to use a dictionary as a key.

Wolverine · Accepted Answer · 2016-06-13 23:06:46Z

0

Just saw the last post, that makes a lot of sense. As far as how this could be useful, I don't know, it was just something I wanted to do, have three values to one key. I'm sure in the future I could take the info from a website or database and have it create pairs, like actors to characters played, but maybe not. It was just something I was annoyed I couldn't figure out on my own.

answered Jun 13, 2016 at 23:06

Wolverine

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