Stuck in a while loop, can you please help?

Question

I am currently writing a program that reads records from a txt file and prints the data on the screen as such:

                       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.

This is the text file it reads from:

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

Here is my code:

# 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.")

The results just print the very last line of the txt file and is stuck in a loop. Any assistance would be greatly appreciated. Thank you for your time.

Answer 1

In this design, "eof" needs to be addded to the globals list in readRecord()

Otherwise assigning it creates a new local variable, which processRecords() never sees.

Answer 2

You have to declare eof as global in readRecord():

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

Otherwise, the changes you make to eof when studentRecord is empty won't survive outside readRecord()'s scope .

Answer 3

You're missing a global here, while your while loop checks the global variable eof, your readRecord function does in fact set the local variable eof.

Answer 4

You need to add eof to the global variables in readRecord():

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

But your solution is a bit un-pythonic. How about something shorter and more flexible:

import re
print ("grade report\n").center(60).upper()
print "name".upper(),"course".rjust(22).upper(),"grade".rjust(32).upper()
print "-" * 60
for line in open("grades.txt"):
    name, course, grade = re.split("   *", line.strip())
    print "%-21s%-34s%-21s" % (name, course, grade)

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

The regular expression is a very simple one that splits on multiple spaces. If you delimiter is something else, then replace the regular expression " *" with your delimiter.

And here is a version that uses python dicts to track the courses and grades by student (i.e. your target output):

import re

print ("grade report\n").center(60).upper()
print "name".upper(),"course".rjust(22).upper(),"grade".rjust(32).upper()
print "-" * 60
grades = {}
total_courses = 0
for line in open("grades.txt"):
    name, course, grade = re.split("   *", line.strip())
    if not grades.get(name): grades[name] = []
    grades[name].append([course, grade])

for name, data in grades.items():
    for course, grade in data:
        print "%-21s%-34s%s" % (name, course, grade)
        name = ""
    print "%-21sTotal courses taken = %d\n" % (" ", len(data))
    total_courses += len(data)

print "Total courses taken by all students = %d" % total_courses

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

BTW, it sounds like you need to learn more about python (and the python way of programming). I recommend Dive Into Python. IMO it's the fastest (and most entertaining) way to come up to speed in python if you are have some programming experience.

Answer 5

Why don't you do it all in a single function -

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

All those functions compressed in this one single function. You seem to be programming much like C code. This is Python!

Also try to avoid using globals unless you must. Just a principle I follow. Clearly in this situation you don't need to.

Answer 6

You have to add eof in the list of globals in readRecord.

However, you said any help, so here's another version:

import itertools as it, operator as op
import collections

Record= collections.namedtuple("Record", "name course grade")
grouper= op.itemgetter(0) # or op.attrgetter('name')

def file_reader(fobj_in):
    for line in fobj_in:
        name= line[:20].rstrip()
        course= line[20:50].rstrip()
        grade= line[50:].rstrip()
        yield Record(name, course, grade)

def process(fn_in, fobj_out):
    for name, records in it.groupby(file_reader(fobj_in), grouper):
        out_name= name
        for index, record in enumerate(records, 1):
            fobj_out.write(
                "%-20.19s%-36.35s%s\n" % (out_name, record.course, record.grade)
            )
            out_name= ''
        fobj_out.write("%20sTotal courses taken = %d\n" % ('', index))

if __name__ == "__main__":
    import sys

    with open('so4009899.txt', 'r') as fobj_in:
        process(fobj_in, sys.stdout)

Answer 7

If you have to use many functions for the purposes of 'structure', consider passing parameters to the functions instead of using globals. Here is a small change that illustrates my meaning.

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

def processRecords():
    numOfRecs = 0
    for line in open("grades.txt","r"):
        numOfRecs += 1
        printLine(line)
    return numOfRecs

def printLine(studentRecord):
    name = studentRecord[0:20]
    course = studentRecord[20:50]
    grade = studentRecord[50:51]
    print name, course.rjust(3), grade.rjust(3)

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


startUp()