删除从文件读取的列表中的换行符[重复]

Question

我有一个简单的程序，它获取一个 ID 号并打印与该 ID 匹配的人的信息。信息存储在 .dat 文件中，每行一个 ID 号。

问题是我的程序也在从文件中读取换行符 \n 。我已经尝试过 'name'.split() 方法，但这似乎不适用于列表。

我的程序：

from time import localtime, strftime

files = open("grades.dat")
request = open("requests.dat", "w")
lists = files.readlines()
grades = []

for i in range(len(lists)):
    grades.append(lists[i].split(","))

cont = "y"

while cont == "y" or cont == "Y":
    answer = raw_input("Please enter the Student I.D. of whom you are looking: ")
    for i in range(len(grades)):
        if answer == grades[i][0]:
            print grades[i][1] + ", " + grades[i][2] + (" "*6) + grades[i][0] + (" "*6) + grades[i][3]
            time = strftime("%a, %b %d %Y %H:%M:%S", localtime())
            print time
            print "Exams - " + grades[i][11] + ", " + grades[i][12] + ", " + grades[i][13]
            print "Homework - " + grades[i][4] + ", " + grades[i][5] + ", " + grades[i][6] + ", " + grades[i][7] + ", " +grades[i][8] + ", " + grades[i][9] + ", " + grades[i][10]
            total = int(grades[i][4]) + int(grades[i][5]) + int(grades[i][6]) + int(grades[i][7]) + int(grades[i][8]) + int(grades[i][9]) + int(grades[i][10]) + int(grades[i][11]) + int(grades[i][12]) + int(grades[i][13])
            print "Total points earned - " + str(total)
            grade = float(total) / 550
            grade = grade * 100
            if grade >= 90:
                print "Grade: " + str(grade) + ", that is equal to an A."
            elif grade >= 80 and grade < 90:
                print "Grade: " + str('%.2f' %grade) + ", that is equal to a B."
            elif grade >= 70 and grade < 80:
                print "Grade: " + str('%.2f' %grade) + ", that is equal to a C."
            elif grade >= 60 and grade < 70:
                print "Grade: " + str('%.2f' %grade) + ", that is equal to a D."
            else:
                print "Grade: " + str('%.2f' %grade) + ", that is equal to an F."
            request.write(grades[i][0] + " " + grades[i][1] + ", " + grades [i][2] +
                          " " + time)
            request.write("\n")


    print
    cont = raw_input("Would you like to search again? ")

if cont != "y" or cont != "Y":
    print "Goodbye."

Answer 1

str.strip() 返回一个删除了前导+尾随空格的字符串，.lstrip 和 .rstrip 分别仅用于前导和尾随。

grades.append(lists[i].rstrip('\n').split(','))

Answer 2

您可以使用strip() 函数删除尾随（和前导）空格；传递一个参数会让你指定哪个空格：

for i in range(len(lists)):
    grades.append(lists[i].strip('\n'))

---

看起来你可以简化整个块，因为如果你的文件每行存储一个 ID，grades 只是 lists 去掉换行符：

之前

lists = files.readlines()
grades = []

for i in range(len(lists)):
    grades.append(lists[i].split(","))

之后

grades = [x.strip() for x in files.readlines()]

（上面是list comprehension）

---

最后，您可以直接遍历列表，而不是使用索引：

之前

for i in range(len(grades)):
    # do something with grades[i]

之后

for thisGrade in grades:
    # do something with thisGrade

Answer 3

您实际上可以通过将整个文件作为单个长字符串读入内存来充分利用换行符，然后使用它们通过使用字符串 splitlines() 方法将其拆分到成绩列表中，默认情况下，删除他们在这个过程中。

with open("grades.dat") as file:
    grades = [line.split(",") for line in file.read().splitlines()]
...

Answer 4

以下是适当的 Python 风格的各种优化和应用，可让您的代码更加整洁。我使用csv 模块添加了一些可选代码，这比手动解析更理想。我还添加了一些 namedtuple 优点，但我不使用随后提供的属性。 namedtuple 各部分的名称不准确，您需要更正它们。

import csv
from collections import namedtuple
from time import localtime, strftime

# Method one, reading the file into lists manually (less desirable)
with open('grades.dat') as files:
    grades = [[e.strip() for e in s.split(',')] for s in files]

# Method two, using csv and namedtuple
StudentRecord = namedtuple('StudentRecord', 'id, lastname, firstname, something, homework1, homework2, homework3, homework4, homework5, homework6, homework7, exam1, exam2, exam3')
grades = map(StudentRecord._make, csv.reader(open('grades.dat')))
# Now you could have student.id, student.lastname, etc.
# Skipping the namedtuple, you could do grades = map(tuple, csv.reader(open('grades.dat')))

request = open('requests.dat', 'w')
cont = 'y'

while cont.lower() == 'y':
    answer = raw_input('Please enter the Student I.D. of whom you are looking: ')
    for student in grades:
        if answer == student[0]:
            print '%s, %s      %s      %s' % (student[1], student[2], student[0], student[3])
            time = strftime('%a, %b %d %Y %H:%M:%S', localtime())
            print time
            print 'Exams - %s, %s, %s' % student[11:14]
            print 'Homework - %s, %s, %s, %s, %s, %s, %s' % student[4:11]
            total = sum(int(x) for x in student[4:14])
            print 'Total points earned - %d' % total
            grade = total / 5.5
            if grade >= 90:
                letter = 'an A'
            elif grade >= 80:
                letter = 'a B'
            elif grade >= 70:
                letter = 'a C'
            elif grade >= 60:
                letter = 'a D'
            else:
                letter = 'an F'

            if letter = 'an A':
                print 'Grade: %s, that is equal to %s.' % (grade, letter)
            else:
                print 'Grade: %.2f, that is equal to %s.' % (grade, letter)

            request.write('%s %s, %s %s\n' % (student[0], student[1], student[2], time))


    print
    cont = raw_input('Would you like to search again? ')

print 'Goodbye.'

Answer 5

您需要 String.strip(s[, chars]) 函数，该函数将去除空格字符或您在 chars 参数中指定的任何字符（例如 '\n'）。

见http://docs.python.org/release/2.3/lib/module-string.html