classmethod 和 staticmethod

我一般很少用到。

Talk is cheap, show you the code.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
##############################################################################
# To explain how to use classmethod and staticmethod.
###############################################################################

# ordinary class
class Date(object):

    def __init__(self, year=0, month=0, day=0):
        self.year = year
        self.month = month
        self.day = day

    def __str__(self):
        return '/'.join([str(x) for x in (self.year, self.month, self.day)])

# class with classmethod and staticmethod
class DateV2(object):

    def __init__(self, year=0, month=0, day=0):
        self.year = year
        self.month = month
        self.day = day

    def __str__(self):
        return '/'.join([str(x) for x in (self.year, self.month, self.day)])

    @classmethod
    def from_string(cls, str_):  # Note, `cls`
        y, m, d = str_.split('-')
        date = cls(y, m, d)
        return date

    @staticmethod
    def data_str_valid(str_):  # note no `self` or `cls`
        y, m, d = str_.split('-')
        return (0 < int(y) <= 9999) and (1 <= int(m) <= 12) and (1 <= int(d) <= 31)

# derive
class DateV3(DateV2):
    pass

if __name__ == '__main__':

    ################################################### test ordinary class
    d = Date(2018, 6, 25)
    print d

    y, m, d = "2018-6-25".split('-')
    d2 = Date(y, m, d)
    print d2

    ################################################## test class with classmethod and staticmethod
    d3 = DateV2(2018, 6, 25)
    print d3

    #dstr = '2018-6-25'
    dstr = '2018-6-32'
    if DateV2.data_str_valid(dstr):
        d4 = DateV2.from_string('2018-6-25')
        print d4
    else:
        print 'dstr invalid!'

    ################################################# test derive
    d5 = DateV3.from_string('2018-6-6')
    print d5

    #dstr = '2018-6-25'
    dstr = '2018-6-32'
    if DateV3.data_str_valid(dstr):
        d6 = DateV3.from_string('2018-6-25')
        print d6
    else:
        print 'dstr invalid!'

Output is，

2018/6/25
2018/6/25
2018/6/25
dstr invalid!
2018/6/6
dstr invalid!

完。