陷入了while循环，请帮忙！

Question

我现在正在写一个程序，这个程序可以从一个文本文件中读取记录，然后把数据打印到屏幕上，像这样：

                       GRADE REPORT

NAME                COURSE                            GRADE
-----------------------------------------------------------
JOE FRITZ           AMERICAN GOVERNMENT                 B
                    CALCULUS I                          A
                    COMPUTER PROGRAMMING                B
                    ENGLISH COMPOSITION                 A
                    Total courses taken = 4

LANE SMITH          FUND. OF DATA PROCESSING            B
                    INTERMEDIATE SWIMMING               A
                    INTRO. TO BUSINESS                  C
                    Total courses taken = 3

JOHN SPITZ          CHOIR                               C
                    COLLEGE STATISTICS                  B
                    ENGLISH LITERATURE                  D
                    INTRO. TO BUSINESS                  B
                    Total courses taken = 4

Total courses taken by all students = 11

Run complete.  Press the Enter key to exit.

这是它读取的文本文件：

JOE FRITZ           AMERICAN GOVERNMENT           B
JOE FRITZ           CALCULUS I                    A
JOE FRITZ           COMPUTER PROGRAMMING          B
JOE FRITZ           ENGLISH COMPOSITION           A
LANE SMITH          FUND. OF DATA PROCESSING      B
LANE SMITH          INTERMEDIATE SWIMMING         A
LANE SMITH          INTRO. TO BUSINESS            C
JOHN SPITZ          CHOIR                         C
JOHN SPITZ          COLLEGE STATISTICS            B
JOHN SPITZ          ENGLISH LITERATURE            D
JOHN SPITZ          INTRO. TO BUSINESS            B

这是我的代码：

# VARIABLE DEFINITIONS

name = ""
course = ""
grade = ""
recordCount = 0
eof = False
gradeFile = ""

#-----------------------------------------------------------------------
# CONSTANT DEFINITIONS

#-----------------------------------------------------------------------
# FUNCTION DEFINITIONS

def startUp():
    global gradeFile
    gradeFile = open("grades.txt","r")
    print ("grade report\n").center(60).upper()
    print "name".upper(),"course".rjust(22).upper(),"grade".rjust(32).upper()
    print "-" * 60
    readRecord()

def readRecord():
    global name, course, grade

    studentRecord = gradeFile.readline()
    if studentRecord == "":
        eof = True
    else:
        name = studentRecord[0:20]
        course = studentRecord[20:50]
        grade = studentRecord[50:51]
        eof = False

def processRecords():
    numOfRecs = 0
    while not eof:
        numOfRecs += 1
        printLine()
        readRecord()
    return numOfRecs

def printLine():
    print name, course.rjust(3), grade.rjust(3)

def closeUp():
    gradeFile.close()
    print "\nTotal courses taken by all students = ",recordCount

#-----------------------------------------------------------------------
# PROGRAM'S MAIN LOGIC

startUp()
recordCount = processRecords()
closeUp()

raw_input("\nRun complete. Press the Enter key to exit.")

但是结果只打印了文本文件的最后一行，而且程序一直在循环中。任何帮助都非常感谢。谢谢你的时间。

Answer 1

在这个设计中，"eof"需要被添加到readRecord()函数的全局变量列表里。

否则，如果只是简单地给它赋值，就会创建一个新的局部变量，而processRecords()函数是看不到这个局部变量的。

Answer 2

你需要在 readRecord() 函数里把 eof 声明为 global：

def readRecord():
    global eof, name, course, grade

否则，当 studentRecord 为空时，你对 eof 所做的修改就无法在 readRecord() 函数外部使用了。

Answer 3

你为什么不把所有的东西都放在一个函数里呢？

def processRecords():
    print ("grade report\n").center(60).upper()
    print "name".upper(),"course".rjust(22).upper(),"grade".rjust(32).upper()
    print "-" * 60

    rec_count = 0
    for line in open("grades.txt","r"):
        name   = line[0:20]
        course = line[20:50]
        grade  = line[50:51]
        print name, course.rjust(3), grade.rjust(3)
        rec_count += 1
    return rec_count

把所有这些功能都压缩到一个函数里。你看起来编程的方式很像C语言的风格。这里是Python啊！

另外，尽量避免使用globals，除非真的需要。我个人遵循这个原则。在这种情况下，显然你并不需要这样做。