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.

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Answer 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)