How do I create a function that will return a value in a dictionary for each row within a data sheet using Python?

Question

I need to create a new column in my table for a state region that populates a region for every row of data (each having a state). How do I write a function to call upon a dictionary for each row item?

I have about 30,000 row items, and I believe a loop would take too long. I am certain there is some way to do this with dictionaries. I've tried using different methods to call this but cannot seem to get it to populate the correct data.

states = {
        'AK': 'Alaska',
        'AL': 'Alabama',
        'AR': 'Arkansas',
        'AZ': 'Arizona',
        'CA': 'California',
        'CO': 'Colorado',
        'CT': 'Connecticut',
        'DC': 'District of Columbia',
        'DE': 'Delaware',
        'FL': 'Florida',
        'GA': 'Georgia',
        'HI': 'Hawaii',
        'IA': 'Iowa',
        'ID': 'Idaho',
        'IL': 'Illinois',
        'IN': 'Indiana',
        'KS': 'Kansas',
        'KY': 'Kentucky',
        'LA': 'Louisiana',
        'MA': 'Massachusetts',
        'MD': 'Maryland',
        'ME': 'Maine',
        'MI': 'Michigan',
        'MN': 'Minnesota',
        'MO': 'Missouri',
        'MS': 'Mississippi',
        'MT': 'Montana',
        'NC': 'North Carolina',
        'ND': 'North Dakota',
        'NE': 'Nebraska',
        'NH': 'New Hampshire',
        'NJ': 'New Jersey',
        'NM': 'New Mexico',
        'NV': 'Nevada',
        'NY': 'New York',
        'OH': 'Ohio',
        'OK': 'Oklahoma',
        'OR': 'Oregon',
        'PA': 'Pennsylvania',
        'RI': 'Rhode Island',
        'SC': 'South Carolina',
        'SD': 'South Dakota',
        'TN': 'Tennessee',
        'TX': 'Texas',
        'UT': 'Utah',
        'VA': 'Virginia',
        'VT': 'Vermont',
        'WA': 'Washington',
        'WI': 'Wisconsin',
        'WV': 'West Virginia',
        'WY': 'Wyoming'
}

state_abbrev = {v: k for k, v in states.items()}

state_code = {
    'AK': '10','AL': '4', 'AR': '9', 'AR': '6', 'CA': '9', 'CO': '8',  'CT': '1', 'DC': '3', 'DE': '3', 'FL': '4',
'GA': '4', 'HI': '9', 'IA': '7', 'ID': '10', 'IL': '5', 'IN': '5', 'KS': '7', 'KY': '4', 'LA': '6', 
'MA': '1', 'MD': '3', 'ME': '1', 'MI': '5', 'MN': '5','MO': '7', 'MS': '4', 'MT': '8', 'NC': '4', 
'ND': '8', 'NE': '7', 'NH': '1', 'NJ': '2', 'NM': '6','NV': '9', 'NY': '2', 'OH': '5', 'OK': '6', 
'OR': '10', 'PA': '3', 'PR': '2', 'RI': '1', 'SC': '4', 'SD': '8', 'TN': '4', 'TX': '6', 'UT': '8',
'VA': '3', 'VI': '2', 'VT': '1', 'WA': '10', 'WI': '5', 'WV': '3', 'WY': '8', 'PI': '9'
    }

state_region = {v: k for k, v in state_code.items()}

def get_region(): return [state_region[i] for i in fulldf['state']]

fulldf["Region"] = get_region() fulldf.tail()

Returns key error 'MA', expected to return a new column named "Region" that populates the region for each "state" listed.

KeyError                                  Traceback (most recent call last)
<ipython-input-338-6afc1e48556a> in <module>
 33     return [state_region[i] for i in fulldf['state']]
 34 
---> 35 fulldf["Region"] = get_region()
 36 fulldf.tail()
 37 

<ipython-input-338-6afc1e48556a> in get_region()
 31 
 32 def get_region():
---> 33     return [state_region[i] for i in fulldf['state']]
 34 
 35 fulldf["Region"] = get_region()

<ipython-input-338-6afc1e48556a> in <listcomp>(.0)
 31 
 32 def get_region():
---> 33     return [state_region[i] for i in fulldf['state']]
 34 
 35 fulldf["Region"] = get_region()

KeyError: 'MA'

Answer 1

Your get_region function is flawed. It should be:

def get_region():
    return [state_region[i] for i in fulldf['state']]

Python comprehensions are optimized enough for that function to be fine for a 30k length dataframe.