原文：https://www.cnblogs.com/skyxiuli/p/10778907.html
    参考：https://www.cnblogs.com/qiuyi21/archive/2008/03/04/1089456.html

    1. import time
    2. #把格式化时间转换成时间戳
    4. def str_to_timestamp(str_time=None, format='%Y-%m-%d %H:%M:%S'):
    5.     if str_time:
    6.         time_tuple = time.strptime(str_time, format)  # 把格式化好的时间转换成元祖
    7.         result = time.mktime(time_tuple)  # 把时间元祖转换成时间戳
    8.         return int(result)
    9.     return int(time.time())
    11. print(str_to_timestamp('2019-04-27 07:01:46'))
    12. print(str_to_timestamp()) #1556349904
    15. # 把时间戳转换成格式化
    17. def timestamp_to_str(timestamp=None, format='%Y-%m-%d %H:%M:%S'):
    18.     if timestamp:
    19.         time_tuple = time.localtime(timestamp)  # 把时间戳转换成时间元祖
    20.         result = time.strftime(format, time_tuple)  # 把时间元祖转换成格式化好的时间
    21.         return result
    22.     else:
    23.         return time.strptime(format)
    25. print(timestamp_to_str(1556348505)) #2019-04-27 15:01:45