I started out with a 4d list, something like

tokens = [[[["a"], ["b"], ["c"]], [["d"]]], [[["e"], ["f"], ["g"]],[["h"], ["i"], ["j"], ["k"], ["l"]]]]

So I converted this to a csv file using the code

import csv
def export_to_csv(tokens):
    csv_list = [["A", "B", "C", word]]
    for h_index, h in enumerate(tokens):
        for i_index, i in enumerate(h):
            for j_index, j in enumerate(i):
                csv_list.append([h_index, i_index, j_index, j])
    
    with open('TEST.csv', 'w') as f:
      
        # using csv.writer method from CSV package
        write = csv.writer(f)

        write.writerows(csv_list)

But now I want to do the reverse process, want to convert a csv file obtained in this format, back to the list format mentioned above.

CodePudding user response：

Assuming you wanted your csv file to look something like this (there were a couple typos in the posted code):

A,B,C,word                                                                          
0,0,0,a                                                                             
0,0,1,b                                                                             
0,0,2,c
...

here's one solution:

import csv                                                                          
                                                                                    
def import_from_csv(filename):                                                      
    retval = []                                                                     
    with open(filename) as fh:                                                      
        reader = csv.reader(fh)                                                     
        # discard header row                                                        
        next(reader)   
        # process data rows                                                             
        for (x,y,z,word) in reader:                                                 
            x = int(x)                                                              
            y = int(y)                                                              
            z = int(z)                                                              
            retval.extend([[[]]] * (x   1 - len(retval)))                           
            retval[x].extend([[]] * (y   1 - len(retval[x])))                       
            retval[x][y].extend([0] * (z   1 - len(retval[x][y])))                  
                                                                                    
            retval[x][y][z] = [word]                                                
                                                                                    
    return retval  

CodePudding user response：

def import_from_csv(file):
    import ast
    import csv

    data = []
    # Read the CSV file
    with open(file) as fp:
        reader = csv.reader(fp)
        # Skip the first line, which contains the headers
        next(reader)
        
        for line in reader:
            # Read the first 3 elements of the line
            a, b, c = [int(i) for i in line[:3]]
            # When we read it back, everything comes in as strings. Use
            # `literal_eval` to convert it to a Python list
            value = ast.literal_eval(line[3])

            # Extend the list to accomodate the new element
            data.append([[[]]]) if len(data) < a   1 else None
            data[a].append([[]]) if len(data[a]) < b   1 else None
            data[a][b].append([]) if len(data[a][b]) < c   1 else None

            data[a][b][c] = value
    return data

# Test
assert import_from_csv("TEST.csv") == tokens