python如何循环执行_如何在python中多次运行for循环？

我正在尝试获取用户输入并交叉引用，以查看它是否在文件中。但是，它只运行for循环一次；如果我在第一次运行时就正确了，如果第一次出错，它就永远不会运行，因为for循环只运行一次。当它为while循环重新运行时，它从不重新运行for循环。为什么python只允许您运行一次循环，我如何解决这个问题？这是密码testDate = open("Sales.txt")

python循环语法，def DateTest(Position):

validSyntax = False

Complete = False

DateIn = True

while Complete == False:

if DateIn == False:

print

print "That date is not in the file."

print

Date = raw_input("Please input the desired %s date in the form YYYY,MM,DD: " % Position)

try :

Date = Date.strip().split(',')

Year = int(Date[0])

Month = int(Date[1])

Day = int(Date[2])

Date = (Year, Month, Day)

except:

print

print "That is invalid input."

print

else:

validSyntax = True

if validSyntax == True:

#It only runs this once, if I put a debug statement after the 'for' #then it never prints out, the loop never runs after the first time

for line in testDate:

line = line.strip().split(',')

yearTest = int(line[0])

monthTest = int(line[1])

dayTest = int(line[2])

dateTest = (yearTest, monthTest, dayTest)

if Date == dateTest:

Complete = True

print 'success'

DateIn = False

validSyntax = False

Response = DateTest("start")