CODEWITHSUNDEEP
pythonpandas
cherrytomato967
cherrytomato967

Reputation: 73

From Pandas series, create dictionary with unique elements as keys, and their indices as values

The goal is to create a dictionary from a pandas column (series) where the keys are the unique elements of the column, and the values are the row indices in which the elements occur. I currently have code that accomplishes this, but I'm wondering if there is a simpler and less hacky way to do it:

df = pd.DataFrame(np.random.randint(0,100,size=(1000, 4)), columns=list('ABCD'))
idx = df['A'].reset_index().groupby('A')['index'].apply(tuple).to_dict()

Upvotes: 4

Views: 929

Answers (2)

ALollz
ALollz

Reputation: 59579

This is the groups attribute of a GroupBy object. It returns a dict with unique values as the keys and Index objects of the Original DataFrame.

df.groupby('A').groups

{0: Int64Index([61, 466, 505, 619, 697, 811, 872], dtype='int64'),
 1: Int64Index([125, 254, 278, 330, 390, 396, 670, 732, 748, 849, 871, 880, 882,
                908, 943], dtype='int64'),
 2: Int64Index([77, 283, 401, 543, 544, 693, 816], dtype='int64'),
 ...}

Or if you really need the tuples:

{k: tuple(v) for k,v in df.groupby('A').groups.items()}

Upvotes: 4

BENY
BENY

Reputation: 323396

You can do 

d = {x : y['index'].tolist() for x , y in df.reset_index().groupby(list(df))}

Upvotes: 1

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