创建文件后，readlines 显示为空

Question

我希望创建一个文件，然后读取我刚刚放入其中的值并将这些值放入列表中。我使用 readlines 来执行此操作，但是我得到“列表分配索引超出范围”错误，告诉我它没有读取文件。

这是我的代码：

import os

class open_saved_file():

    def __init__(self):
        self.path = os.getcwd()
        self.path_extension = "/Saved_Paths"
        self.file_extension = "/Paths.txt"
        self.paths = []

    def test_path(self):

        test_bool = os.path.exists(self.path+self.path_extension)
#1) path does not exist
        if not test_bool:
            print "The start folder does not exist, let's create it"
            os.makedirs(self.path+self.path_extension)
            print "just made file, now make Paths.txt"
            of = open(self.path+self.path_extension+self.file_extension, 'w+')
            print "Lets add 4 dummy lines of code"
            i = 0
            while i < 4:
                of.write("dummy\n")
                i = i+1
            print "just added four lines of dummy"
            of.close()
            print "lets test"
            self.read_lines_into_list()
            return self.paths
#2) path and file exist
        else:
            print "The start folder did exist, yay!"
            print "lets open it and put its value into paths list"
            self.read_lines_into_list()
            return self.paths

    def read_lines_into_list(self):
        of = open(self.path+self.path_extension+self.file_extension)
        lines = of.readlines()
        self.paths[0] = lines[0][:-1]
        self.paths[1] = lines[1][:-1]
        self.paths[2] = lines[2][:-1]
        self.paths[3] = lines[3][:-1]
        print "lets test if all the values went in"
        j = 0
        while j < 4:
            print self.paths[j]
            i = i+1

Answer 1

发生错误不是因为lines 为空，而是因为self.paths 为空。而不是：

self.paths[0] = lines[0][:-1]

使用append():

self.paths.append(lines[0][:-1])

您的while 循环中也会出现错误，因为当您的循环变量为j 时，您正在执行i = i+1。您可以简单地将i 替换为j，或者更好的是，使用for 循环：

for path in self.paths:
    print path

Answer 2

您还可以添加对 os.path.isfile 的调用以验证文件是否存在。

Answer 3

这里是修改后的代码。

import os
class OpenSavedFile():
def __init__(self):
    self.path = os.getcwd()
    self.path_extension = "/Saved_Paths"
    self.file_extension = "/Paths.txt"
    self.paths = []

def test_path(self):
    test_bool = os.path.exists(self.path+self.path_extension)
    if not test_bool:
        print "The start folder does not exist, let's create it"
        os.makedirs(self.path+self.path_extension)
        print "just made file, now make Paths.txt"
        of = open(self.path+self.path_extension+self.file_extension, 'w+')
        print "Lets add 4 dummy lines of code"
        i = 0
        while i < 4:
            of.write("dummy\n")
            i = i+1
        print "just added four lines of dummy"
        of.close()
        print "lets test"
        self.read_lines_into_list()
        return self.paths
    else:
        print "The start folder did exist, yay!"
        print "lets open it and put its value into paths list"
        self.read_lines_into_list()
        return self.paths

def read_lines_into_list(self):
    of = open(self.path+self.path_extension+self.file_extension)
    lines = of.readlines()
    # lines is not empty 
    # remove the comment below and see
    # print lines
    for line in lines:
        self.paths.append(line[:-1]) # paths is an empty list so append the contents
    print "lets test if all the values went in"
    j = 0
    while j < 4:
        print self.paths[j]
        j += 1 # this is not i += 1

op = OpenSavedFile()
op.test_path()