Getting a TypeError: 'Series' objects are mutable, thus they cannot be hashed when using a function to convert a int in a column to a season

Question

I have a data-frame called 'temperatures' that contains a month column with the values of 1 - 12 and I have written a function to take the month number and return the season for the Southern Hemisphere where the data is taken from.

def find_season(month):

    season_month = {
    12:'Summer', 1:'Summer', 2:'Summer',
    3:'Autumn', 4:'Autumn', 5:'Autumn',
    6:'Winter', 7:'Winter', 8:'Winter',
    9:'Spring', 10:'Spring', 11:'Spring'}
    return season_month.get(month)

I would like to achieve the following output

Year    Month   Season                          
1955    2       Summer
1955    3       Autumn
1955    7       Winter
1955    12      Summer

But when I go to fill the Season column using my formula

temperatures['Season'] = temperatures.apply(find_season(temperatures.Month))
OR
temperatures['Season'] = find_season(temperatures.Month)

I get the error

TypeError: 'Series' objects are mutable, thus they cannot be hashed.

I would rather use a function as I feel this code could be useful for other analyses I am doing but cannot figure out how to get around the issue I am facing.

Answer 1

The error is saying that the key in a dict has to be a constant, immutable object, like the strings in your example or a number.

I can't see how you would get that error from that code, so I would guess it's an example and in your real code you were doing temperatures[x] and x is a variable that points to a Series object and that's the problem; objects of type Series are not constants and therefore can't be used as keys in a dict.

Answer 2

Here is the solution:

def find_season(month):
    season_month = {
    12:'Summer', 1:'Summer', 2:'Summer',
    3:'Autumn', 4:'Autumn', 5:'Autumn',
    6:'Winter', 7:'Winter', 8:'Winter',
    9:'Spring', 10:'Spring', 11:'Spring'}
    return season_month.get(month)

temperatures={}
temperatures["Month"]=[1,2,3,4,5,6,7,8,9,10,11,12]
seasonlist=[]
for month in temperatures["Month"]:
    season = find_season(month)
    seasonlist.append(season)

temperatures["Season"] = seasonlist
print(temperatures)

Output:

{'Month': [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], 'Season': ['Summer', 'Summer', 'Autumn', 'Autumn', 'Autumn', 'Winter', 'Winter', 'Winter', 'Spring', 'Spring', 'Spring', 'Summer']}

So you have several errors in your code, one is that you are trying to get a Month property from the temperatures dictionary ( temperatures.Month ), you should refer to its key value instead: temperatures["Month"]

The other issue is that temperatures["Month"] is a list, and you are passing it to a function that takes a single number instead. You need to iterate through the array of month in order to get the season for each month.