使用python的if语句正确使用地图功能

Question

我尝试正确使用映射并使用的是if语句，以确保如果列表为空，以不进行并停止。我也将显示输入。为了澄清，数字_1函数是我使用地图选项的地方。我需要编辑什么才能完成这项工作？我对如何解决此问题感到困惑，我的代码在下面是我的代码

#this is the input file    
#John Jackson
#91 94 38 48 70 85 94 59
#James Johnson
#78 96 90 55 77 82 94 60
#Edward Kinsley
#99 94 82 77 75 89 94 93
#Mozilla Firefox
#49 92 75 48 80 95 99 98    
def lab8():
    userinput= "Lab8.txt"
    lenoffile= len(userinput)
    print "There is", lenoffile, "lines"
    File= open (userinput, "r")
    studentscores1= File.read()
    studentlist= studentscores1.split("\n")
    return studentlist, lenoffile
def Names_1(studentlist, lenoffile):
    print "=============================="
    ai = ""
    for i in range (0, lenoffile, 2):
        ai += studentlist[i] + "\n"
    print "===============below is ai=========="
    print ai
    return ai
def Numbers_1(studentlist, lenoffile):    
    bi= ""
    for i in range (1, lenoffile, 2):
        bi += studentlist[i] + "\n"
    bi = bi.split ("\n")
    print bi
    return bi
    print "====================BELOW IS THE SCORE========================="
def Outputfile_1(ai):
    outputfile= raw_input ("What is the output file.txt:")
    File2= open(outputfile, "w")
    File2.write(ai)
    return outputfile

def numbers_1(bi):
    for b1 in bi:
        b1 = b1.split(" ")
        lenofb1 = len(b1)
        quiztotalb = 0
        midtermb = 0
        Final = 0
        if lenofb1 > 0:
            b1 = map(int, b1)
            quiztotal = ((b1[0] + b1[1] + b1[2] + b1[3] + b1[4])/5)
            midtermtotal = ((b1[5]) + b1[6])/2
            Finaltotal = (b1[7])
            Score = (quiztotal*.3 + midtermtotal*.4 + Finaltotal*.3)
            print Score
def main():    
    studentlist, lenoffile = lab8()
    ai = Names_1(studentlist, lenoffile)
    bi = Numbers_1(studentlist, lenoffile)
    #outputfile = Outputfile_1(ai)
    numbers_1(bi)
main()

我得到了 ValueError: invalid literal for int() with base 10: ''我一直在努力，我不确定应该从这里去哪里。

Answer 1

You are splitting b1 on single spaces, and this can lead to empty values:

>>> '88  89 '.split(' ')
['88', '', '89', '']

It is the extra empty strings here that cause int() to throw an exception:

>>> int('')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: ''

Use str.split() with no argument instead; extra whitespace is then stripped:

>>> '88  89 '.split()
['88', '89']

You have some other problems as well in your code. Take a good look at:

def lab8():
    userinput= "Lab8.txt"
    lenoffile= len(userinput)
    print "There is", lenoffile, "lines"
    File= open (userinput, "r")
    studentscores1= File.read()
    studentlist= studentscores1.split("\n")
    return studentlist, lenoffile

Here, lenoffile is not the number of lines in the file. It is the number of characters in 'Lab8.txt'; both values happen to be 8, but add or remove some lines from that file and the number will be wrong for the rest of your code.

If you are supposed to keep these numbers together with the names and write out the calculations again, you'll have to do some work keeping the names together.

Here is an alternative version to solve the same task:

outputfile = raw_input("What is the output filename? :")

with open('Lab8.txt') as infile, open(outputfile, 'w') as outtfile:
    for name in infile:
        scores = next(infile).split()  # next() grabs the next line from infile here
        scores = map(int, scores)

        quiztotal = sum(scores[:4]) / 5
        midtermtotal = sum(scores[5:7]) / 2
        finaltotal = scores[7]
        score = quiztotal * .3 + midtermtotal * .4 + finaltotal * .3

        outfile.write(name)
        outfile.write('{0:0.2f}\n'.format(score))