1.判断回文

类似‘aa','aba','abcba','abccba'就是回文

def huiwen(char):
    length=len(char)
    for i in range(length//2):
        if char[i] != char[length-1-i]:
            return False
    return True

# 使用递归
def huiwen(char):
    print(char)
    length=len(char)
    if length <= 1:
        return True
    else:
        return char[0] == char[-1] and huiwen(char[1:-1])

2.利用sort函数的key关键字排序

class Tu():
    def __init__(self, name, amount):
        self.name = trader
        self.amount = amount


data = [
    Tu('d',10000000),
    Tu('a', 1000),
    Tu('b',10000),
    Tu('c',100000),
]

# 通过匿名函数传入要排序的项
def sort_by_amount(data):
    data.sort(key=lambda x:x.amount)
    return data

3. 检查一个日期，跟当月某个星期几的关系

from datetime import datetime


def _parse(date):
    """
    :param date: string '20180911'
    :return: datetime
    """
    return datetime.strptime(date, "%Y%m%d")


def _check_day(date, day=5):
    """
    判定是否是星期几
    :param date: datetime
    :param day: int,周一为1，周五为5，周天为7
    :return:
    """
    return date.weekday() + 1 == day


def _count_days(date):
    """
    计算日期当月有多少天
    :param date: datetime
    :return: int
    """
    year = date.year
    month = date.month
    if month == 12:
        next_month = 1
        next_year = year + 1
    else:
        next_month = month + 1
        next_year = year
    return (datetime(next_year, next_month, 1) - datetime(year, month, 1)).days


def _check_date(date, num, day):
    """
    日期有没有过该月第几个周几
    :param date: string 例如'20180101'
    :param num: int，第几个"day"
    :param day: int，周几，周一是1，周五是5，周天是7
    :return:
    """
    count = 0
    flag = None
    date = _parse(date)
    days = _count_days(date)
    for i in range(1, days):
        the_day = datetime(date.year, date.month, i)
        if _check_day(the_day, day):
            count += 1
        if count == num:
            flag = the_day
            break
    if flag and date > flag:
        return True
    else:
        return False


def CheckDate(date):
    return _check_date(date, 3, 5)