如何通过在中间插入/更改字符来修改文本文件？

Question

I'm trying to write a code that modifies certain text in a text file. I want it to write to a different file not append the old file. The.replace function does not work because I'm not replacing a certain word with another word. I'm doing math operations to a certain part of the file, then I want the new file to contain the new information.

I tried reading each line, looping through the lines and writing the code I want by slicing the line, but its not working. The code does not change anything in the text file.

This is the code:

filename = "timetag.txt"
fileout = "converted_timetag.txt"

old = open(filename,'r')
lines = old.readlines()
new = open(fileout,'w')

for line in lines:
    time = int(line[6:15])*20
    newlines = [str(line[:6]) + str(time) + "\n"]
    new.write(newlines)

old.close()
new.close()

Answer 1

In the line newlines = [str(line[:6]) + str(time) + "\n"] you use the [ ] , which attempts to make newlines into a list . This gives an error during runtime,

TypeError: write() argument must be str, not list

Since new.write(newlines) needs to take a string, not a list.

You can fix this error by taking out the square brackets, like so: newlines = str(line[:6]) + str(time) + "\n" .

Your code would look like:

filename = "timetag.txt"
fileout = "converted_timetag.txt"

old = open(filename,'r')
lines = old.readlines()
new = open(fileout,'w')

for line in lines:
    time = int(line[6:15])*20
    newlines = str(line[:6]) + str(time) + "\n"
    new.write(newlines)

old.close()
new.close()

If timetag.txt contains:

time: 123456789
time: 100000000
time: 000000001
time: 000000002

The output is:

time: 2469135780
time: 2000000000
time: 20
time: 40