如何在文本文件的特定列位置添加或替换某些字符串

Question

How to add or replace some string at a particular column position in a text file: for example i have one sentence in a particular file example given below:

Roxila almost lost
Roxila almost lost
Roxila almost lost
Roxila almost lost
Roxila almost lost

"enumerate()" gives some thing like this

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
R o x i l a   a l m  o  s  t     l  o  s  t 

now i want to mutate index "6" which is a "space" with "*" at each row. like this:

Roxila*almost lost

how can i do this with python. Please help

Answer 1

You can use slicing to get a new string and fileinput module to update the existing file:

Slicing demo:

>>> s = "Roxila almost lost"
'Roxila almost lost'
>>> s [:6] + '*' + s[7:]
'Roxila*almost lost'

Updating the file:

import fileinput
for line in fileinput.input('foo.txt', inplace=True):
    print line[:6] + '*' + line[7:],

Answer 2

for line in f:
   line = line.rstrip()
   newline = line[:6] + '*' + line[7:]
   print newline

Answer 3

Another approach, using replace

with open("yourfile.txt", "r") as file:
    lines = file.read().split("\n")
    newlines = []
    for line in lines:
        newline = line.replace(" ", "*", 1)
        newlines.append(newline)

with open("newfile.txt", "w") as newfile:    
    newfile.write("\n".join(newlines))

Answer 4

If your first string change, which means the length, in that case slicing won't work:

Better to use this way:

>>> s.split(' ')
['Roxila', 'almost', 'lost']
>>> p = s.split(' ')
>>> p[0]+'*'+' '.join(p[1:])
'Roxila*almost lost'
>>>