python,datetime 时间格

import datetime,re
def parse_date(date_str):
    try:
        if not date_str:
            return None
        if "-" in date_str:
            if date_str.count("-") == 1:
                date = datetime.datetime.strptime(date_str, "%Y-%m")
            elif date_str.count("-") == 2:
                date = datetime.datetime.strptime(date_str, "%Y-%m-%d")
        elif "年" in date_str:
            if "日" in date_str:
                date = datetime.datetime.strptime(date_str, "%Y年%m月%d日")
            elif "月" in date_str:
                date = datetime.datetime.strptime(date_str, "%Y年%m月")
            else:
                date = datetime.datetime.strptime(date_str, "%Y年")
        elif date_str.isdigit():
            if len(date_str) == 4:
                date = datetime.datetime.strptime(date_str, "%Y")
            elif len(date_str) > 6:
                date = datetime.datetime.strptime(date_str, "%Y%m%d")
            else:
                date = datetime.datetime.strptime(date_str, "%Y%m")
        else:
            date = None
    except:
        return None
    return date

date_reg_v1 = re.compile(r"\d+年\d+月\d+日")
date_reg_v2 = re.compile(r"\d+年\d+月")
date_reg_v3 = re.compile(r"\d+-\d+-\d+")
date_reg_v4 = re.compile(r"\d+-\d+")
str =' 2199年10月 '
# 正则去掉多余的
kk = date_reg_v2.search(str).group()
kk =parse_date(kk)
print(kk)