2025-09-10:仓库迁移

3.数字日期和时间/13.计算上周五的日期.py

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+from datetime import datetime, timedelta
+
+if __name__ == '__main__':
+    weekdays = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
+
+    def get_previous_by_day(day_name, start_date=None):
+        if start_date is None:
+            start_date = datetime.today()
+
+        day_num = start_date.weekday()
+        day_num_target = weekdays.index(day_name)
+
+        days_ago = (7 + day_num - day_num_target) % 7
+
+        if days_ago == 0:
+            days_ago = 7
+        target_date = start_date - timedelta(days=days_ago)
+        return target_date
+
+    get_previous_by_day("Friday")
+
+    # 但是如果要经常这么干，请使用dateutil包
+    d = datetime.now()
+    from dateutil.relativedelta import relativedelta
+    from dateutil.rrule import *
+
+    # 找最近的周五，FR是rrule里的函数
+    print(d + relativedelta(weekday=FR))
+
+    # 找上一个周五
+    print(d + relativedelta(weekday=FR(-1)))