Python 基础 - 为什么我的文件内容不打印？

Question

我从 eclipse 运行这个，我正在使用的文件名是 ex16_text.txt(是的，我输入正确。它正确地写入文件(输入出现)，但是“print txt.read ()"似乎没有做任何事情(打印一个空行)，查看代码后的输出:

filename = raw_input("What's the file name we'll be working with?")

print "we're going to erase %s" % filename

print "opening the file"
target = open(filename, 'w')

print "erasing the file"
target.truncate()

print "give me 3 lines to replace file contents:"

line1 = raw_input("line 1: ")
line2 = raw_input("line 2: ")
line3 = raw_input("line 3: ")

print "writing lines to file"

target.write(line1+"\n")
target.write(line2+"\n")
target.write(line3)

#file read
txt = open(filename)

print "here are the contents of the %s file:" % filename
print txt.read()

target.close()

输出:

我们将使用的文件名是什么？ex16_text.txt我们要删除 ex16_text.txt打开文件删除文件给我 3 行来替换文件内容:第 1 行:三个第 2 行:两个第 3 行:一个将行写入文件以下是 ex16_text.txt 文件的内容:

Answer 1

你应该 flush写入文件以确保字节已写入。另请阅读警告:

Note: flush() does not necessarily write the file’s data to disk. Use flush() followed by os.fsync() to ensure this behavior.

如果您已完成对文件的写入并想以只读访问权限再次打开它，您也应该关闭该文件。请注意，关闭文件也会刷新 - 如果关闭文件，则不需要先刷新。

在 Python 2.6 或更新版本中，您可以使用 with 语句自动关闭文件:

with open(filename, 'w') as target:
    target.write('foo')
    # etc...

# The file is closed when the control flow leaves the "with" block

with open(filename, 'r') as txt:
    print txt.read()