Question

I have a program which let the user input som data which then get drawn on the canvas (like a weekly scheme).
I now want the user to be able to delete or redo an entry (which i will do by a click event), however, my question goes:

How do i read a specific line in my textfile? A sample of a possible textfile:

Abe
#0080c0 
February
Friday 
21 
Part delivery 

John 
#ff8000 
July 
Sunday 
21 
Social 

Egon 
#ff80ff 
April 
Thursday 
15 
Work 

Note that this is a small part of the textfile, ideally it would contain 56 of theese 6-line-clusters.

my code for inserting the text:

taskentry = str(tasknameentry.get())
monthentry = str(monthvar.get())
dayentry = str(dayvar.get())
dateentry = str(datevar.get())
activityentry = str(typevar.get())

tasklist = [taskentry, hexstr, monthentry, dayentry, dateentry, activityentry]
taskfile = open('taskfile.txt', 'a')
for word in tasklist:
    taskfile.write('%s \n' % word)
taskfile.write('\n')
taskfile.close()

So for the user to be able to redo or delete a “task” i need to read the file and look for a specific task name or something similar, im just not sure how to. I’ve read through the .write and .read part of my book, looked at the docs and questions here but havent been able to produce a valid solution.

What i need now, so i can move on is just a way to read fx the 6 appending lines when searching for fx John. So i in the future can have a redo or delete event choosen by a click.

In advance, thanks!

Best regards,
Casper

Answer 1

If the file is not that big, you can read the file into a buffer, modify that buffer and write the buffer back to the file. A quick code snippet would be like:

#open the file
f = open('file.txt')
lines = f.readlines()
lineNum = -1

#find the line to modify
for i, line in enumerate(lines):
    if line.strip() == "John":
        lineNum = i
        break

if lineNum == -1:
    #Line not found, handle the error..

#modify the buffer with the new data
newtasklist = [taskentry, hexstr, monthentry, dayentry, dateentry, activityentry]
for task in newtasklist:
    lines[lineNum] = task
    lineNum += 1

#or if you want to remove the task list :
lines = lines[:lineNum] + [lineNum + 7:]

# and write everything back
with open('file.txt', 'w') as file:
    file.writelines(lines)