Python高效计算上周五到任意日期的完全指南

from datetime import datetime, timedelta

def get_last_friday():
    """计算上周五日期"""
    today = datetime.today()
    # 计算到上周五的天数偏移
    # 周一(0)到周日(6)，周五是4
    offset = (today.weekday() - 4) % 7
    if offset == 0:  # 今天就是周五
        offset = 7
    return today - timedelta(days=offset)

# 使用示例
last_fri = get_last_friday()
print(f"上周五日期: {last_fri.strftime('%Y-%m-%d')}")

def get_last_weekday(target_weekday):
    """
    计算上周指定星期几的日期
    :param target_weekday: 0=周一, 1=周二, ..., 6=周日
    """
    today = datetime.today()
    # 计算日期偏移
    offset = (today.weekday() - target_weekday) % 7
    if offset == 0:  # 今天就是目标日
        offset = 7
    return today - timedelta(days=offset)

# 使用示例
last_monday = get_last_weekday(0)  # 上周一
last_friday = get_last_weekday(4)  # 上周五

class BusinessDateCalculator:
    """工作日计算器（考虑节假日）"""
    def __init__(self, holidays=None):
        self.holidays = holidays or set()
    
    def add_holiday(self, date):
        """添加节假日"""
        self.holidays.add(date)
    
    def is_business_day(self, date):
        """检查是否为工作日"""
        # 周末检查
        if date.weekday() >= 5:  # 5=周六, 6=周日
            return False
        # 节假日检查
        return date not in self.holidays
    
    def last_business_day(self, date=None):
        """计算上一个工作日"""
        date = date or datetime.today()
        while True:
            date -= timedelta(days=1)
            if self.is_business_day(date):
                return date
    
    def last_specific_weekday(self, target_weekday, date=None):
        """计算上一个指定星期几（考虑节假日）"""
        date = date or datetime.today()
        # 先找到上一个目标星期几
        candidate = get_last_weekday(target_weekday, date)
        # 如果不是工作日，继续向前找
        while not self.is_business_day(candidate):
            candidate -= timedelta(days=7)
        return candidate

# 使用示例
calculator = BusinessDateCalculator()
# 添加节假日（示例）
calculator.add_holiday(datetime(2023, 12, 25))  # 圣诞节

last_biz_fri = calculator.last_specific_weekday(4)  # 上一个周五（工作日）
print(f"上一个工作日周五: {last_biz_fri.strftime('%Y-%m-%d')}")

from datetime import datetime
import pytz

def get_last_friday_tz(timezone='Asia/Shanghai'):
    """时区敏感的上周五计算"""
    # 获取时区
    tz = pytz.timezone(timezone)
    # 获取当前时区时间
    now = datetime.now(tz)
    
    # 计算偏移
    offset = (now.weekday() - 4) % 7
    if offset == 0:  # 今天就是周五
        offset = 7
    
    # 计算上周五
    last_fri = now - timedelta(days=offset)
    return last_fri

# 使用示例
shanghai_fri = get_last_friday_tz('Asia/Shanghai')
newyork_fri = get_last_friday_tz('America/New_York')

print(f"上海时区上周五: {shanghai_fri.strftime('%Y-%m-%d %H:%M')}")
print(f"纽约时区上周五: {newyork_fri.strftime('%Y-%m-%d %H:%M')}")

class PayrollSystem:
    """工资结算系统"""
    def __init__(self):
        self.payday_weekday = 4  # 周五发薪
        self.cutoff_day = 1       # 每月1日结算
    
    def calculate_pay_period(self, date=None):
        """计算工资结算周期"""
        date = date or datetime.today()
        
        # 计算结算日（每月1日）
        if date.day >= self.cutoff_day:
            cutoff_date = datetime(date.year, date.month, self.cutoff_day)
        else:
            # 上个月
            prev_month = date.replace(day=1) - timedelta(days=1)
            cutoff_date = datetime(prev_month.year, prev_month.month, self.cutoff_day)
        
        # 计算发薪日（最近周五）
        payday = self._get_nearest_weekday(cutoff_date, self.payday_weekday)
        
        # 计算工资周期
        start_date = cutoff_date - timedelta(days=30)  # 上个月结算日
        return start_date, cutoff_date, payday
    
    def _get_nearest_weekday(self, date, target_weekday):
        """获取指定日期后最近的星期几"""
        # 计算偏移
        offset = (target_weekday - date.weekday()) % 7
        if offset == 0:  # 当天就是目标日
            return date
        return date + timedelta(days=offset)

# 使用示例
payroll = PayrollSystem()
start, cutoff, payday = payroll.calculate_pay_period()

print(f"工资周期: {start.strftime('%Y-%m-%d')} 至 {cutoff.strftime('%Y-%m-%d')}")
print(f"发薪日: {payday.strftime('%Y-%m-%d')}")

def stock_settlement_date(trade_date):
    """计算股票交易结算日 (T+2)"""
    from pandas.tseries.offsets import BDay
    
    # 转换为pandas时间戳
    trade_date = pd.Timestamp(trade_date)
    
    # 计算T+2工作日
    settlement_date = trade_date + 2 * BDay()
    return settlement_date.date()

# 使用示例
trade_date = datetime(2023, 12, 20)  # 周三
settlement = stock_settlement_date(trade_date)
print(f"交易日期: {trade_date.strftime('%Y-%m-%d')}")
print(f"结算日期: {settlement.strftime('%Y-%m-%d')}")  # 周五

class WeeklyReportGenerator:
    """周报表生成系统"""
    def __init__(self, start_weekday=0):  # 默认周一为一周开始
        self.start_weekday = start_weekday
    
    def get_last_week_range(self, date=None):
        """获取上周日期范围"""
        date = date or datetime.today()
        # 找到本周开始日期
        start_offset = (date.weekday() - self.start_weekday) % 7
        this_week_start = date - timedelta(days=start_offset)
        
        # 上周开始和结束
        last_week_start = this_week_start - timedelta(weeks=1)
        last_week_end = last_week_start + timedelta(days=6)
        
        return last_week_start.date(), last_week_end.date()
    
    def generate_report(self, report_date=None):
        """生成周报表"""
        start, end = self.get_last_week_range(report_date)
        print(f"生成周报表: {start} 至 {end}")
        # 实际报表生成逻辑
        # ...

# 使用示例
reporter = WeeklyReportGenerator(start_weekday=0)  # 周一为周开始
reporter.generate_report()

# 指定日期生成
custom_date = datetime(2023, 12, 25)  # 圣诞节
reporter.generate_report(custom_date)

def fiscal_month_range(date=None, fiscal_start_day=26):
    """计算财务月范围（上月26日到本月25日）"""
    date = date or datetime.today()
    
    if date.day >= fiscal_start_day:
        # 本月26日到下月25日
        start = datetime(date.year, date.month, fiscal_start_day)
        end_month = date.month + 1 if date.month < 12 else 1
        end_year = date.year if date.month < 12 else date.year + 1
        end = datetime(end_year, end_month, fiscal_start_day) - timedelta(days=1)
    else:
        # 上月26日到本月25日
        prev_month = date.replace(day=1) - timedelta(days=1)
        start = datetime(prev_month.year, prev_month.month, fiscal_start_day)
        end = datetime(date.year, date.month, fiscal_start_day) - timedelta(days=1)
    
    return start.date(), end.date()

# 使用示例
start_date, end_date = fiscal_month_range()
print(f"财务月范围: {start_date} 至 {end_date}")

class DeliveryCalculator:
    """交货日期计算器"""
    def __init__(self, production_days=5, shipping_days=3):
        self.production_days = production_days
        self.shipping_days = shipping_days
        self.holidays = set()
    
    def add_holiday(self, date):
        """添加节假日"""
        self.holidays.add(date)
    
    def calculate_delivery_date(self, order_date):
        """计算预计交货日期"""
        from pandas.tseries.offsets import BDay
        
        # 生产完成日期
        production_end = order_date + self.production_days * BDay()
        
        # 运输日期（自然日）
        delivery_date = production_end + timedelta(days=self.shipping_days)
        
        # 检查是否为节假日
        while delivery_date.weekday() >= 5 or delivery_date in self.holidays:
            delivery_date += timedelta(days=1)
        
        return delivery_date

# 使用示例
calculator = DeliveryCalculator(production_days=7, shipping_days=2)
calculator.add_holiday(datetime(2023, 12, 25).date())  # 圣诞节

order_date = datetime(2023, 12, 18).date()  # 周一
delivery = calculator.calculate_delivery_date(order_date)

print(f"下单日期: {order_date}")
print(f"预计交货日期: {delivery}")

def inventory_cycle_date(base_date=None, cycle_days=7):
    """计算库存盘点日期"""
    base_date = base_date or datetime.today().date()
    
    # 找到最近的上周五
    last_friday = get_last_weekday(4, base_date)
    
    # 计算下一个盘点日
    next_cycle = last_friday + timedelta(days=cycle_days)
    
    # 如果是周末则调整到周一
    if next_cycle.weekday() >= 5:
        next_cycle += timedelta(days=7 - next_cycle.weekday())
    
    return next_cycle

# 使用示例
next_inventory_date = inventory_cycle_date(cycle_days=10)
print(f"下次盘点日期: {next_inventory_date.strftime('%Y-%m-%d')}")

class DateCalculator:
    """高级日期计算工具"""
    def __init__(self, base_date=None):
        self.base_date = base_date or datetime.today()
    
    def last_occurrence(self, weekday=None, day=None, month=None):
        """
        计算上次出现的日期
        :param weekday: 星期几 (0-6)
        :param day: 每月几号
        :param month: 月份
        """
        if weekday is not None:
            return self._last_weekday(weekday)
        elif day is not None:
            return self._last_month_day(day)
        elif month is not None:
            return self._last_year_month(month)
        else:
            raise ValueError("必须指定一个条件")
    
    def _last_weekday(self, target_weekday):
        """计算上一个指定星期几"""
        offset = (self.base_date.weekday() - target_weekday) % 7
        if offset == 0:
            offset = 7
        return self.base_date - timedelta(days=offset)
    
    def _last_month_day(self, target_day):
        """计算上一个指定日期（每月几号）"""
        if self.base_date.day >= target_day:
            # 本月有该日期
            return datetime(self.base_date.year, self.base_date.month, target_day)
        else:
            # 上个月
            prev_month = self.base_date.replace(day=1) - timedelta(days=1)
            return datetime(prev_month.year, prev_month.month, target_day)
    
    def _last_year_month(self, target_month):
        """计算上一个指定月份"""
        if self.base_date.month >= target_month:
            return datetime(self.base_date.year, target_month, 1)
        else:
            return datetime(self.base_date.year - 1, target_month, 1)

# 使用示例
calc = DateCalculator(datetime(2023, 12, 20))

print("上周五:", calc.last_occurrence(weekday=4).strftime('%Y-%m-%d'))
print("上月5号:", calc.last_occurrence(day=5).strftime('%Y-%m-%d'))
print("去年3月:", calc.last_occurrence(month=3).strftime('%Y-%m-%d'))

from flask import Flask, jsonify, request

app = Flask(__name__)

@app.route('/api/last-date', methods=['GET'])
def last_date_api():
    """日期计算API"""
    # 获取参数
    date_type = request.args.get('type')
    target = request.args.get('target')
    base_date = request.args.get('date')
    
    # 解析日期
    base_date = datetime.strptime(base_date, '%Y-%m-%d') if base_date else datetime.today()
    
    # 计算日期
    calculator = DateCalculator(base_date)
    try:
        if date_type == 'weekday':
            result = calculator.last_occurrence(weekday=int(target))
        elif date_type == 'day':
            result = calculator.last_occurrence(day=int(target))
        elif date_type == 'month':
            result = calculator.last_occurrence(month=int(target))
        else:
            return jsonify({'error': 'Invalid type'}), 400
    except Exception as e:
        return jsonify({'error': str(e)}), 400
    
    return jsonify({
        'result': result.strftime('%Y-%m-%d'),
        'base_date': base_date.strftime('%Y-%m-%d')
    })

# 启动服务
if __name__ == '__main__':
    app.run(port=5000)

# 测试API
# GET /api/last-date?type=weekday&target=4&date=2023-12-20
# 返回: {"result": "2023-12-15", "base_date": "2023-12-20"}

# 所有日期操作前转换为UTC
utc_time = datetime.now(pytz.utc)
# 操作后转换回本地时间
local_time = utc_time.astimezone(pytz.timezone('Asia/Shanghai'))

# 使用pandas BusinessDay
from pandas.tseries.offsets import BDay
next_biz_day = datetime.today() + BDay(1)

# 批量日期计算向量化
import numpy as np
import pandas as pd

dates = pd.date_range('2023-01-01', periods=100000)
# 向量化计算上周五
offsets = np.where(dates.weekday >= 4, dates.weekday - 4, dates.weekday + 3)
last_fridays = dates - pd.to_timedelta(offsets, unit='D')

def safe_date_calculation(func):
    """日期计算错误处理装饰器"""
    def wrapper(*args, **kwargs):
        try:
            return func(*args, **kwargs)
        except OverflowError:
            return datetime.max
        except ValueError as e:
            if 'day is out of range' in str(e):
                # 处理月末日期
                base = args[0]
                last_day = (base.replace(day=28) + timedelta(days=4)).replace(day=1) - timedelta(days=1)
                return last_day
            raise
    return wrapper

def get_last_weekday(target_weekday, base_date=None):
    """
    计算上一个指定星期几

    参数:
        target_weekday: 目标星期几 (0=周一, 6=周日)
        base_date: 基准日期 (默认今天)

    返回:
        上一个目标星期几的日期

    示例:
        >>> get_last_weekday(4)  # 上周五
        datetime.date(2023, 12, 15)
    """
    base_date = base_date or datetime.today()
    # ...实现代码

import unittest
from datetime import date

class TestDateCalculations(unittest.TestCase):
    def test_last_friday(self):
        # 测试周五当天
        self.assertEqual(get_last_weekday(4, date(2023, 12, 15)), date(2023, 12, 8))
        # 测试周六
        self.assertEqual(get_last_weekday(4, date(2023, 12, 16)), date(2023, 12, 15))
        # 测试周日
        self.assertEqual(get_last_weekday(4, date(2023, 12, 17)), date(2023, 12, 15))
        # 测试周一
        self.assertEqual(get_last_weekday(4, date(2023, 12, 18)), date(2023, 12, 15))

    def test_edge_cases(self):
        # 月初测试
        self.assertEqual(get_last_weekday(4, date(2023, 1, 1)), date(2022, 12, 30))
        # 闰年测试
        self.assertEqual(get_last_weekday(4, date(2024, 2, 29)), date(2024, 2, 23))