Replace line in file contents

Question

How to open a file, Stud.txt, and then replace any occurrences of "A" with "Orange"?

Answer 1

with open("Stud.txt", "rt") as fin: with open("out.txt", "wt") as fout: for line in fin: fout.write(line.replace('A', 'Orange')) 

Answer 2

If you want to replace the lines in the same file, you probably have to read its contents into a local variable, close it and open it again for writing:

In this example, I use the with statement , which closes the file after the with block completes - usually after the last command completes, or by exception.

 def inplace_change(filename, old_string, new_string): # Safely read the input filename using 'with' with open(filename) as f: s = f.read() if old_string not in s: print('"{old_string}" not found in {filename}.'.format(**locals())) return # Safely write the changed content, if found in the file with open(filename, 'w') as f: s = f.read() print('Changing "{old_string}" to "{new_string}" in {filename}'.format(**locals())) s = s.replace(old_string, new_string) f.write(s) 

It is worth noting that if the file names were different, we could do it more elegantly with a single with statement.

Answer 3

  #!/usr/bin/python with open(FileName) as f: newText=f.read().replace('A', 'Orange') with open(FileName, "w") as f: f.write(newText) 

Answer 4

Something like

 file = open('Stud.txt') contents = file.read() replaced_contents = contents.replace('A', 'Orange') <do stuff with the result> 

Answer 5

 with open('Stud.txt','r') as f: newlines = [] for line in f.readlines(): newlines.append(line.replace('A', 'Orange')) with open('Stud.txt', 'w') as f: for line in newlines: f.write(line) 

Answer 6

If you are using Linux and just want to replace the word " dog with" cat you can do the following:

text.txt:

 Hi, i am a dog and dog are awesome, i love dogs! dog dog dogs! 

Linux command:

 sed -i 's/dog/cat/g' test.txt 

Exit:

 Hi, i am a cat and cat are awesome, i love cats! cat cat cats! 

Original post: https://askubuntu.com/questions/20414/find-and-replace-text-within-a-file-using-commands

Answer 7

The easiest way to do this is with regular expressions, assuming that you want to iterate over each line in the file (where "A" will be stored).

 import re input = file('C:\full_path\Stud.txt), 'r') #when you try and write to a file with write permissions, it clears the file and writes only #what you tell it to the file. So we have to save the file first. saved_input for eachLine in input: saved_input.append(eachLine) #now we change entries with 'A' to 'Orange' for i in range(0, len(old): search = re.sub('A', 'Orange', saved_input[i]) if search is not None: saved_input[i] = search #now we open the file in write mode (clearing it) and writing saved_input back to it input = file('C:\full_path\Stud.txt), 'w') for each in saved_input: input.write(each)