Explain a piece of code

[SuuzyQ04]

Hi there,

Could someone please explain very clearly what the following piece of code is doing?

def question_set(X):
    qset = [[] for col in X[0]]
    for row in X:
        for i,col in enumerate(row):
            qset[i].append(col)
    
    return [set(row) for row in qset]

question_set(X_train)

I'm quite new to this, so I thank you greatly!

Larz60+ write Nov-19-2020, 04:04 PM:
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[Gribouillis]

This function takes as an argument an object X which is a sequence of rows of some array-like structure. Here is what it does:

1. It uses the first row X[0] to determine the number of columns of the array and it creates a sequence of empty lists, one for each column.
   
2. For each row of X, it appends each element of the row to the list of the corresponding column.
   
3. At the end, it transforms every such created column into a set instance, thus elimitating duplicate items and forgetting the order in which they appear in the column.
   
4. It returns finally the sequence of sets, each of them containing a unique instance of every value found in the columns of the initial array-like structure.
   

IMHO, the whole function could be simplified into

def question_set(X):
    return [set(c) for c in zip(*X)]