添加到日期，检查是否过期

Question

我的程序的一部分要求用户输入一个日期，然后对照字典中的每个产品检查该日期，以查看产品到达日期加上其保质期是否会导致产品在输入日期之前或之后过期由用户。

import sys
from string import *
import pickle
import datetime

cheeseDictionary = {}
userInput = ""

def loadProduct(fileName):
    global cheeseDictionary
    f = open(fileName,"r")
    line = f.readline()         # Reads line from file
    while line:
        line = line[:-1]
        data = split(line,":")  # Splits line when there is a colon
        cheeseDictionary[data[0]] = {"date":data[1], "life":data[2], "name":data[3]} # Stores each split item
        line = f.readline()     # Next line
    f.close()

def saveProduct(fileName,cheeseDictionary): 
    f = open(fileName, "w")
    for i in sorted(cheeseDictionary.keys()):
        v = cheeseDictionary[i]
        f.write("%s:%s:%s:%s\n" % (i, v["date"], v["life"], v["name"]))
    f.close()

def printProduct(cheeseDictionary):
    print "ID"," ","Date"," ","Life(days)"," ","Name"
    for cheese in cheeseDictionary:
        print cheese," ",cheeseDictionary[cheese]["date"]," ",cheeseDictionary[cheese]["life"],"    ",cheeseDictionary[cheese]["name"]

def addProduct():
    global cheeseDicitonary
    correct = 0
    idInput = ""
    dateInput = ""
    lifeInput = ""
    nameinput = ""

    while correct != 1:
        idInput = raw_input("Please enter the ID of the cheese to be added. ")
        if cheeseDictionary.has_key(idInput):
            print ("This ID already exists. Please try again.")
            correct = 0
        else:
            newID = idInput
            correct = 1
    dateInput = raw_input("Please enter the date of the cheese to be added in the format dd/mm/yyyy. ")
    lifeInput = raw_input("Please enter the life of the cheese to be added in days. ")
    nameInput = raw_input("Please enter the name of the cheese to be added. ")
    cheeseDictionary[idInput] = {"date":dateInput, "life":lifeInput, "name":nameInput}

def checkProduct(cheeseDictionary):
    dateCheck = raw_input("Please enter the date in the format dd/mm/yyyy: ")
    for cheese in cheeseDictionary:

我知道我需要将字典中存储的日期更改为日期时间格式，但我不确定如何执行此操作。感谢您提供的任何建议。 :)

Answer 1

如果我理解正确，您需要将表示“dd/mm/yyyy”格式的日期的字符串转换为日期时间对象吗？

如果是这样，您应该使用datetime.strptime 方法。例如：

from datetime import datetime
d = datetime.strptime("28/03/2011", "%d/%m/%Y")
print repr(d)

打印出来：

datetime.datetime(2011, 3, 28, 0, 0)

Answer 2

为了将日期字符串解析为datetime 对象，可以使用strptime 方法：

http://www.tutorialspoint.com/python/time_strptime.htm

您需要了解的有关 Python 的几乎所有内容都可以在文档中找到。这是datetime的文档：

http://docs.python.org/library/datetime.html

至于日期数学（加法和减法），它们可以通过在 datetime 对象中添加或减去 timedelta 对象来完成。以下是允许的操作：

datetime2 = datetime1 + timedelta
datetime2 = datetime1 - timedelta
timedelta = datetime1 - datetime2
datetime1 < datetime2

所有详细信息都可以在上面链接中的文档页面上找到。

还有一个关于日期数学的小教程：

http://phr0stbyte.blogspot.com/2008/08/python-datetime-math.html

Answer 3

为了它，我已经做了一个非常全面的面向对象的重写：

import datetime

class Date(object):
    def __init__(self, s):
        if isinstance(s, Date):
            self.date = s.date
        elif isinstance(s, datetime.date):
            self.date = s
        else:
            self.date = datetime.datetime.strptime(s, "%d/%m/%Y")

    def __add__(self, val):
        if isinstance(val, Life):
            val = val.life
        elif not isinstance(val, datetime.timedelta):
            val = datetime.timedelta(val)
        return self.__class__(self.date + val)

    def __cmp__(self, val):
        return (self.date - val.date).days

    def __str__(self):
        return self.date.strftime("%d/%m/%Y")

class Life(object): 
    def __init__(self, s):
        if isinstance(s, Life):
            self.life = s.life
        elif isinstance(s, datetime.timedelta):
            self.life = s
        else:
            self.life = datetime.timedelta(days=int(s))

    def __str__(self):
        return str(self.life.days)

class Product(object):
    FMT = "{0:10} {1:10} {2:24}".format

    def __init__(self, date, life, name):
        super(Product,self).__init__()
        self.date = Date(date)
        self.life = Life(life)
        self.name = str(name).strip()

    def __str__(self):
        return Product.FMT(self.date, self.life, self.name)

    def expires(self):
        return Date(self.date + self.life)

    @classmethod
    def get(cls):
        date = getClass(Date, "Please enter the date (DD/MM/YYYY): ")
        life = getClass(Life, "Please enter the life (in days): ")
        name = raw_input("Please enter the name of the cheese: ")
        return cls(date, life, name)

    def vals(self):
        return self.date, self.life, self.name

class FileOf(object):
    def __init__(self, cls):
        self.data = {}
        self.cls  = cls

    def loadFile(self, fname, mode='r', sep=':'):
        _data = self.data
        _cls  = self.cls
        with open(fname, mode) as inf:
            for line in inf:
                try:
                    items = line.strip().split(sep)
                    id = items.pop(0)
                    _data[id] = _cls(*items)
                except ValueError, e:
                    print(e)
        return self

    def saveFile(self, fname, mode='w', sep=':', eol='\n', key=None):
        _data = self.data
        keys = _data.keys()
        keys.sort(key=key)
        with open(fname, mode) as outf:
            for id in keys:
                outf.write(str(id)+sep)
                outf.write(sep.join(str(v) for v in _data[id].vals()))
                outf.write(eol)
        return self

    def addNew(self):
        id  = getNewKey(self.data, "Please enter the new ID: ")
        obj = getClass(self.cls)
        self.data[id] = obj
        return self

    def printAll(self, key=None):
        _data = self.data
        _cls  = self.cls
        ID = "{0:4} ".format
        print ID("id") + _cls.FMT("Date", "Life", "Name")
        keys = _data.keys()
        keys.sort(key=key)
        for id in keys:
            print ID(id) + _cls.FMT(*(_data[id].vals()))
        return self

    def filter(self, filterFn):
        newFile = FileOf(self.cls)
        newFile.data = {id:item for id,item in self.data.iteritems() if filterFn(id, item)}
        return newFile

def getNewKey(keys, msg='', keytype=str):
    "Prompt for a key not already in keys"
    while True:
        key = keytype(raw_input(msg))
        if key in keys:
            print("This key already exists. Please try again.")
        else:
            return key

def getClass(cls, *args, **kwargs):
    "Return a new instance of given class; prompt for required values"
    if hasattr(cls, 'get'):
        # if the class knows how to 'get' itself, let it
        return cls.get(*args, **kwargs)
    else:
        # otherwise we assume the class knows how to init itself from a string
        while True:
            s = raw_input(*args)
            try:
                return cls(s, **kwargs)
            except ValueError, e:
                print(e)

def getExpired(cheeses, asOf=None):    
    asOf = Date(asOf) if asOf else getClass(Date, "Please enter expiration test date (DD/MM/YYYY): ")
    return cheeses.filter(lambda id,obj: obj.expires() <= asOf)

def main():
    cheeses = FileOf(Product).loadFile('cheesefile.txt')
    cheeses.printAll()

    cheeses.addNew()

    expiredA = getExpired(cheeses)                 # prompt for expiration date
    expiredB = getExpired(cheeses, "12/3/2011")    # use given date

    print("The expired items are:")
    expiredB.printAll()

    cheeses.saveFile('cheesefile.txt')

if __name__=="__main__":
    main()

还有一个示例 cheesefile.txt 文件：

ab:03/01/2011:10:brie
ac:03/01/2001:20:camembert
de:01/03/2011:30:brie
fg:01/03/2011:1:blink and it's gone
hi:01/05/2011:200:hard white cheddar
jkl:01/04/2011:60:jarlsberg