'''
    DS2000
    Fall 2024
    Starter code for class on 11/1/24

    There's a little starter code in here, and then we're going
    to add in two more functions:
    1. row_to_dct
        parameters - two lists of strings, row & keys, same length
                     (the first list is a row from the csv file,
                     the second is a list of keys which are the header of the csv file)
        returns - a dictionary of strings where key comes from second list,
                  value comes from first list
        does - creates an empty dictionary, then iterates by position over list of keys.
               Every keys[i] becomes a key in the dictionary, with value row[i]

    2. count_greater
        parameters - two lists of dictionaries, string for column name,
                     int for threshold
        returns - an int, the number of values in the given column >
                  the given threshold
        does - iterates over the list of dictionaries. In each dictionary,
               looks in the given column (col name will be the key). If the value
               is > given threshold, increment the count
'''

import csv

FILENAME = "1920-voter_registration.csv"

def csv_to_lst_of_dct(filename):
    '''
        parameter: filename, a string
        returns: list of dictionaries (all key/value pairs are strings)
        does: creates a list of dictionaries where each dictionary represents
              one row from the CSV file. Dictionary keys are from the header of
              the csv file, and dictionary values are from the rows.
    '''
    data = []
    with open(filename, 'r') as infile:
        csvfile = csv.reader(infile)
        keys = next(csvfile)
        for row in csvfile:
            dct = row_to_dct(row, keys)
            data.append(dct)
    return data

def row_to_dct(row, keys):
    '''
        params: 2 lists of strings (one row from csv file, one list of keys)
        returns: a dictionary where keys come from one list, and values from the other
        does: turns lists into key/value pairs
    '''
    dct = {}
    for i in range(len(row)):
        k = keys[i]
        v = row[i]
        dct[k] = v
    return dct

def count_greater(lst_of_dct, col_name, mn_val):
    '''
        params: list of dictionaries, col name (string), mn_value (number)
        return: an int
        does: count the number of values in teh given column greater than
            the minimum value
    '''
    count = 0
    for dct in lst_of_dct:
        val = int(dct[col_name])
        if val > mn_val:
            count += 1
    return count

def main():
    # step one: gather data by turning CSV file into
    # list of dictionaries
    lst_of_dct = csv_to_lst_of_dct(FILENAME)

    # step one cont'd: gather data by prompting user
    # for minimum age to look for in voter list
    age = int(input("What age to look for?\n"))

    # step two: computation, count the number of women
    # registered to vote who were over the given age
    count = count_greater(lst_of_dct, "Age", age)

    # step three: communicate by printing the count
    print(count, "women over age", age, "registered!")
main()