问题
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.
回答1:
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.
回答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 .
回答3:
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.
回答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.
回答5:
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.
回答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)
回答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()
来源：https://stackoverflow.com/questions/4009899/stuck-in-a-while-loop-can-you-please-help