On 11/29/2011 10:09 AM, Mic wrote:
Hey again.
<SNIP most of lengthy code sample>
root=Tk()
root.title("testV2")
app=Mainwindow(root)
root.mainloop()
What's that code got to do with the question below?
I am now writing another program. It turned out just fine, but I have
one question.
If button one is pressed I want the program to write, say hi_1, on the
first line in a text file.
If button one is pressed again, the first line should be empty.
If button two is pressed I want the program to write hi_2 in the
second line in the text file.
If button two is pressed again, the second line in the text file
should be empty.
You can't in general write randomly to a text file, especially if the
line length changes.
If button three is pressed I want the program to write hi_3 in the
third line in the text file.
if button three is pressed again, the third line in the text file
should be empty.
There shouldn't be any other changes to the program other than this
above. There is already a text file
created, the program doesn't need to create one. We can call that file
"Hi".
I hope you understand what I want to do here. I have tried the entire
evening yesterday to get this to work, I tried using writeline() but I
can't get it to work.
What are your suggestions to this?
You have at least three choices:
1) abandon the notion of a text file for this purpose. Make it a
structured (binary) file, with fixed length fields.
2) same thing, but fake it in a text file, either by changing the
contents so it's always the same size, or putting in redundant blanks.
3) reconstruct the entire file every time you want to change a line
(other than the last one) to something larger or smaller.
For #3,
If the file is only about 3 lines, keep a list in memory, and dump the
whole list to the file every time you change one of the items.
For #1 and #2, you should look up the seek() method of the file class.
--
DaveA
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