此“文件打开”代码有什么问题？

Question

I am not able to open an excel file to write data using following code in python 2.7.3. What is wrong with this code?

def openfile():
    import os
    f=open('ab.xls', 'w')
    return

import Tkinter
from Tkinter import *
root=Tk()
root.geometry('100x100+100+100')

button1=Button(root, text='Open file', command=openfile)
button1.pack()

root.mainloop()

Thanks

Answer 1

1. Putting import os inside the function means it doesn't get imported until you run the function... probably not what you want.

2. You open the file, but never return a handle to it. Try replacing return with return f

3. If you are using import xlwt , you don't need this anyway; it takes care of writing to a file. See my previous response at How to export user inputs (from python) to excel worksheet?

Edit:

... 'ab.xls' was opened, you returned a handle to it, and then do nothing with it . What did you expect it to do, exactly?

Try

import Tkinter as tk

def do_something_with_file():
    with open('ab.xls', 'w') as f:
        print("The file is open")
        # --> now DO SOMETHING with it <--

root = tk.Tk()
root.geometry('100x100+100+100')
button1 = tk.Button(root, text='Open file', command=do_something_with_file)
button1.pack()
root.mainloop()

Answer 2

You seem to be confused about what open means in this context. open() is a function that returns a file handle in Python so you can read the data into your application.

If you want to open the file with the default program on your system for that filetype, look into os.startfile() .

Answer 3

Your "f" variable is a file object that is a local variable (destroyed as soon as the "openfile" function ends). You can either declare f as global, or have your openfile function return the file object.

Answer 4

i can't see any obvious fatal errors in this code.

going out on a limb here, especially if you are running this on windows, is the file perhaps still open somewhere else, like in excel or through your own code? you can not open a file for writing if it already is open for writing elsewhere.