#!/usr/bin/env python3

"""

# Purpose: Make a CSV file showing the number of instances of a key field

# Customize: Set KEY_FIELD, MIN_KEY_COUNT

# Python: Use python or python3 below as appropriate to your system; verify that you have version 3.9 or greater

# $ python -V or python3 -V

# Python 3.x.y

# Usage:

# 1: Generate a CSV file KeyValues.csv

# 2: From that CSV file, output a CSV file with headers "Key,Count" that shows the

# number of instances if each key value

# $ python3 CountKeyValues.py ./KeyValues.csv ./KeyValueCounts.csv

"""

import csv

import sys

QUOTE_CHAR = '"' # Adjust as needed

LINE_TERMINATOR = '\n' # On Windows, you probably want '\r\n'

KEY_FIELD = '' # Set to a column header in KeyValues.csv

MIN_KEY_COUNT = 0 # 0 - Show all counts; N - Show counts >= N

if (len(sys.argv) > 2) and (sys.argv[2] != '-'):

outputFile = open(sys.argv[2], 'w', encoding='utf-8', newline='')

else:

outputFile = sys.stdout

outputCSV = csv.DictWriter(outputFile, ['Key', 'Count'], lineterminator=LINE_TERMINATOR, quotechar=QUOTE_CHAR)

outputCSV.writeheader()

if (len(sys.argv) > 1) and (sys.argv[1] != '-'):

inputFile = open(sys.argv[1], 'r', encoding='utf-8')

else:

inputFile = sys.stdin

keyCounts = {}

for row in csv.DictReader(inputFile, quotechar=QUOTE_CHAR):

keyValue = row[KEY_FIELD]

keyCounts.setdefault(keyValue, 0)

keyCounts[keyValue] += 1

for key, count in sorted(keyCounts.items()):

if count >= MIN_KEY_COUNT:

outputCSV.writerow({'Key': key, 'Count': count})

if inputFile != sys.stdin:

inputFile.close()

if outputFile != sys.stdout:

outputFile.close()