将格式为YYMMDD的VARCHAR转换为YYYYMMDD并忽略无效的日期格式

import re

def convert_date(date_str):
    match = re.match(r'^(\d{2})(\d{2})(\d{2})$', date_str)
    
    if match:
        year = int(match.group(1))
        month = int(match.group(2))
        day = int(match.group(3))
        
        current_year = 2022  # 假设当前年份为2022
        
        if year < 100:
            # 转换两位数的年份为四位数
            if year <= current_year % 100:
                year += current_year // 100 * 100
            else:
                year += (current_year // 100 - 1) * 100
                
        if 1 <= month <= 12 and 1 <= day <= 31:  # 仅作简单的日期有效性检查，实际应根据具体月份和年份进行更精确的判断
            return '{:04d}{:02d}{:02d}'.format(year, month, day)
    
    return None  # 无效的日期格式

# 示例用法
date_str = '220731'
converted_date = convert_date(date_str)
if converted_date:
    print('转换后的日期为:', converted_date)
else:
    print('无效的日期格式')