Question

I am trying to replace a string with a new string in a python file and write the new string permanently to it. When I run the below script it removes part of the string and not all of it. The string in the file is:

self.id = "027FC8EBC2D1"

And the script I have to replace the string is:

def edit():

    o = open("test.py","r+") #open 
    for line in open("test.py"):   
        line = line.replace("027FC8EBC2D1","NewValue")  
        o.write(line) 
    o.close()

edit()

Thanks for any help.

Answer 1

The proper way to do (actually simulate😉 “in-place substitution” on text files with Python is the fileinput module:

import fileinput

for line in fileinput.input(['test.py'], inplace=True):
  print line.replace('027FC8EBC2D1', 'NewValue'),

Note a couple of crucial details wrt the other answer that suggests the same module: input‘s first argument must be a list of filenames (not a string!), and, you do have to print every line that you want in the resulting file (fileinput redirects standard output to perform — actually simulate — the “overwrite in-place” effect).

A final small but not-negligible detail: the comma at the end of the print statement is to avoid adding another newline at the end (since each line already ends with a newline!-).