python中如何使用datetime模块

import datetimeimport calendar#第一个例子：#算一下还有多久能还清信用卡#定义信用卡待还总额10000元balance = 10000#定义利率为13%interest_rate = 13 * .01#定义每个月还500元monthly_payment = 500#获取今天today = datetime.date.today()#print(today)#获取本月有多少天days_in_current_month = calendar.monthrange(today.year,today.month)[1]#返回一个元组#第一个参数是本周的第几天#第二个参数是本月有多少天print(days_in_current_month)#获取还有几天到月末days_till_end_month = days_in_current_month - today.dayprint(days_till_end_month)#获取下个月的开始日期#作为我们第一次还款月start_date = today + datetime.timedelta(days=days_till_end_month + 1) print(start_date)#定义还款日期等于开始还款日期end_date = start_datewhile balance >0:  #获取产生利息的费用  interest_charge = (interest_rate / 12) * balance  #需要还款的总额  balance += interest_charge  #减去已还额度，剩余待还  balance -=monthly_payment  #四舍五入保留两位小数字  balance = round(balance,2)   if balance < 0:    balance = 0  #打印还款月，剩余待还金额  print(end_date,balance)  #获取还款月的总天数  days_in_current_month = calendar.monthrange(end_date.year,end_date.month)[1]  #获取下一还款月  end_date = end_date + datetime.timedelta(days=days_in_current_month) 
#运行就可以查看到需要多少个月还清信用卡了
#第二个例子：#算一下多少周可以减肥到目标体重#当前体重150斤current_weight = 150#目标体重100斤goal_weight = 100#假设一周减掉1.5斤avg_lose_weight_week = 1.5#获取开始日期 start_date = datetime.date.today()#定义达到目标体重的结束日期end_date = start_datewhile current_weight > goal_weight:  current_weight -= avg_lose_weight_week  end_date  += datetime.timedelta(days=7) print(end_date)print(f'达到目标体重需要{(end_date - start_date).days // 7} 周！')
#第三个例子#计算什么时间粉丝可以达到100000#目标粉丝数量goal_subs = 100000#当前粉丝数量current_subs = 85000#还需多少粉丝到目标subs_to_goal = goal_subs - current_subs#假设每天粉丝增长为200个avg_subs_day = 200import math#计算需要多少天达到目标days_to_goal = math.ceil(subs_to_goal/avg_subs_day) #计算哪天达到目标today = datetime.date.today()goal_subs_date = today + datetime.timedelta(days=days_to_goal)print(goal_subs_date)