透视csv并保留不带pandas的键列

import csv
from collections import defaultdict

def pivot_csv(input_file, output_file, key_col, pivot_col, value_col):
    # 读取CSV文件并创建透视表
    pivot_table = defaultdict(lambda: defaultdict(int))
    
    with open(input_file, 'r') as csvfile:
        reader = csv.DictReader(csvfile)
        for row in reader:
            key = row[key_col]
            pivot_value = row[pivot_col]
            value = int(row[value_col])
            pivot_table[key][pivot_value] += value
    
    # 将透视表写入新的CSV文件
    with open(output_file, 'w', newline='') as csvfile:
        fieldnames = ['Key'] + list(pivot_table[next(iter(pivot_table))].keys())
        writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
        
        writer.writeheader()
        for key, values in pivot_table.items():
            row = {'Key': key}
            row.update(values)
            writer.writerow(row)

# 示例用法
pivot_csv('input.csv', 'output.csv', 'KeyColumn', 'PivotColumn', 'ValueColumn')