How to change first character in each line of a text file?

Question

I want to change the first character on each line in the text file. Here is my code and my output but I don't know how to change and save that in the same text file.

for rf in glob.glob('./labels/train/*'):
    read=open(rf,'r')
    t=read.readlines()
    for ind in t:
        print(ind[0])

I have got what I want but I don't know how to change that and save it in the same text file.

1 0.7141610738255033 0.7547281921618205 0.401006711409396 this is the data. I only want to change the first int. i want that first 1 to be zero on each line. — tornike
– tornike, Commented May 8, 2022 at 15:20

Sharim09 · Accepted Answer · 2022-05-08 15:40:59Z

1

Try this:)

for rf in glob.glob('./labels/train/*'):
    read=open(rf,'r')
    t=read.readlines()

    read.close()
    for_write = [str(int(ind[0])-1)+ind[1:] for ind in t]   
    write = open(rf,'w')
    write.writelines(for_write)
    write.close()

or using with:)

for rf in glob.glob('./labels/train/*'):
    with open('test.txt','r')as read:
        t=read.readlines()
        for_write = [str(int(ind[0])-1)+ind[1:] for ind in t]
    with open('test.txt','w') as write:
        write.writelines(for_write)

edited May 8, 2022 at 15:40

answered May 8, 2022 at 15:24

Sharim09

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4 Comments

tornike Over a year ago

It does not change the values and deletes other values in txt file.

tornike Over a year ago

I want to change only the first char. others should be the same. i want to subtract 1 on every first int on each line.

Sharim09 Over a year ago

@tornike you want 1 23423.34 23424 to 0 23423.34 23424 am I right or not.

tornike Over a year ago

yes. exactly. on each line. one more problem is that , these numbers in txt are string

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