Python中的程序代码“不在”状态下不工作

Question

这个代码每次都返回不在文件中的日期，我不知道为什么。你知道吗

testDate = open("Sales.txt")

#Declaring variables for later in the program
printNum = 1

newcost = 0

startTestLoop = 1

endTestLoop = 1

#Creating a loop in case input is invalid
while startTestLoop > 0:

    #Asking user for start date
    #startDate = raw_input("Please input the desired start date in the form YYYY,MM,DD: ")


    #Checking if input is valid, and arranging it to be used later
    try :
        startDate = startDate.strip().split(',')
        startYear = startDate[0]
        startMonth = startDate[1]
        startDay = startDate[2]
        startYear = int(startYear)
        startMonth = int(startMonth)
        startDay = int(startDay)
        startDate = date(startYear, startMonth, startDay)
    #Informing user of invalid input
    except:
        "That is invalid input."
        print
    #EndTry



    #Testing to see if date is in the file, and informing user
    if startDate not in testDate:
        print "That date is not in the file."
    #Exiting out of loop if data is fine 
    else:
        startTestLoop -= 1
        print "Aokay"
    #EndIf

Answer 1

 #assume your Sales.txt contains a list of dates split by space
  if startDate not in testDate.read().split():
        print "That date is not in the file."

Answer 2

表达式not in测试iterable（列表、元组甚至字符串）中元素的成员身份。如果一个日期（或任何其他相关内容）在一个打开的文件中，它的工作原理与您在测试中假设的不一样。您必须逐行遍历文件并询问日期（作为字符串）是否在一行中，那里您可以使用not in。你知道吗

编辑：

如评论中所建议的，您可以使用：

f = open("Sales.txt")
testDate = f.read()
f.close()

。。。但是无论如何，您需要确保文件中的日期和代码中的日期都使用相同的字符串格式。你知道吗