Question

这是我的代码：

from os.path import exists

def confirm(file_name):
    while not exists(file_name):
        print "File doesn't exist."
        file_name = raw_input("File name: ")

from_file = raw_input("copy from: ")
confirm(from_file)
to_file = raw_input("copy to: ")
confirm(to_file)

with open(to_file, 'w')as f:
    f.write(open(from_file).read())

终端输出

copy from: asd.txt
File doesn't exist.
File name: test.txt
copy to: dsa.txt
File doesn't exist.
File name: test.py
Traceback (most recent call last):
  File "ex17.py", line 17, in <module>
    f.write(open(from_file).read())
IOError: [Errno 2] No such file or directory: 'ad.txt'

为什么打开错误的文件？

如何解决？

当我这样做时：

   from_file = raw_input("copy from: ")
   while not exists(from_file):
       print "File doesn't exist."
       from_file = raw_input("File name: ")

效果很好。

我想为更少的代码定义一个函数，但是我遇到了问题。

Answer 1

我会在内部修改函数来处理raw_input，你可以做类似这样的事情，它将循环while输入不是现有文件，并且如果它是现有文件。

from os.path import exists

def getFileName(msg):
    file_name = raw_input(msg)
    while not exists(file_name):
        print "File {} doesn't exist. Try again!".format(file_name)
        file_name = raw_input(msg)
    return file_name

from_file = getFileName("copy from: ")
to_file = getFileName("copy to: ")

with open(to_file, 'w') as f:
    f.write(open(from_file).read())

注意这假设两个文件都已存在。如果您的目的是在运行时创建 to_file，我们需要进行一些修改。如果是这样的话，请告诉我......

Answer 2

您在file_name内对confirm所做的更改不会影响您传递给该功能的参数。您应该在file_name中返回confirm的最终值，并让调用者将其分配给相应的变量。

Answer 3

删除第11行（确认（to_file）），新文件无法存在

我认为你可以使用它：

with open('file.txt', 'r') as f:
    with open('newfile.txt', 'w') as nf:
        nf.write(f.read())

我不明白为什么不能在Python 2.x中正确打开（）文件

3 个答案: