Python中CSV文件所有列的唯一元素，不使用Pandas

Question

I am trying to get the unique values of all the columns in the CSV. I am getting the column number and creating sets for all the columns and trying to go through the csv data and find the unique columns. But the second loop executes only once.

decoded_file = data_file.read().decode('utf-8')
reader = csv.reader(decoded_file.splitlines(),
                            delimiter=',')
list_reader = list(reader)
data = iter(list_reader)
next(data) #skipping the header
col_number = len(next(data))
col_sets = [set() for i in range(col_number)]

for col in range(col_number):
   for new_row in data:
       col_sets[col].add(new_row[col])
   print(col_sets[col])

I need to get all the unique values for each column and add it to col_sets to access it. What is the best way to do this?

Answer 1

Everything is good, but you should just change the order of iterations.

for new_row in data:
    for col in range(col_number):
        col_sets[col].add(new_row[col])
print(col_sets)