Replace exact match word with specific string in python

Question

I am completely new to Python and this is my first script to replace word.

my file test.c contains following two lines

printf("\nReboot not supported.  Exiting instead.\n");
fprintf(stderr, "FATAL:  operation not supported!\n");

Now I want to replace printf and fprintf by //printf and //fprintf respectively.

Here is what I have tried

infile = open('path\to\input\test.c')
outfile = open('path\to\output\test.c', 'w')

replacements = {'printf':'//printf', 'fprintf':'//fprintf'}

for line in infile:
    for src, target in replacements.iteritems():
        line = line.replace(src, target)
    outfile.write(line)
infile.close()
outfile.close()

But using this I got

fprintf to //f//printf which is wrong.

For the solution have looked this answer but not able to fit it in my script.

Anyone have idea how can I fix it?

score 5 · Accepted Answer · answered Jan 29 '15 at 06:01

Basically you want to convert printf to //printf and fprintf to //fprintf. If that's the case then this might work, try it out.

  outfile = open("test.c", 'r')
  temp = outfile.read()
  temp = re.sub("printf", "//printf", temp)
  temp = re.sub("f//printf", "//fprintf", temp)
  outfile.close()
  outfile = open("test.c","w")
  outfile.write(temp)
  outfile.close()

score 0 · Answer 2 · answered Jan 29 '15 at 05:40

0

dict in python is not ordered. so you cannot guarantee print or fprintf will be picked up first while traversing dict in the following line:

for src, target in replacements.iteritems():

In the current case, print looks to be picked first thats why you are facing the issue. In order to avoid the issue, either use orderdict or keep list of dicts for replacements.

answered Jan 29 '15 at 05:40

venpa

4,268
21
23

How can use `Orderdict`? Have tried by `OrderedDict(sorted(replacements.items(), key=lambda t: t[0]))` but getting error for undefined `OrderedDict`. – Jayesh Bhoi Jan 29 '15 at 05:51

score 0 · Answer 3 · answered Jan 29 '15 at 05:42

0

Here's what it's doing. The dictionaries are not ordered (as you may think they are) so the fprintf replacement actually comes first and then it replaces the printf portion of it. Sequence:

fprintf -> //fprintf -> //f//printf

answered Jan 29 '15 at 05:42

Kyle Coventry

555
3
9

So how can i avoid this? – Jayesh Bhoi Jan 29 '15 at 05:43
Using orderdict as mentioned above will allow you to utilize a dictionary that adheres to the key ordering it was entered with, or you can use a list instead. Should solve the issue. – Kyle Coventry Jan 29 '15 at 05:44
@Jayesh to avoid that, you can you list or, tuple instead of dict `[('printf','//printf'), ('fprintf','//fprintf')]` – dragon2fly Jan 29 '15 at 05:46
@dragon2fly Tried by `replacements = [{'printf':'//printf', 'fprintf':'//fprintf'}]` but got error like `AttributeError: 'list' object has no attribute 'iteritems'`. – Jayesh Bhoi Jan 29 '15 at 05:50
Careful with your brackets. Curly brackets indicate a dictionary... You want the rounded ones. – Kyle Coventry Jan 29 '15 at 05:52
@Jayesh you still use dict inside a list, that cause error. `replacements =[('printf','//printf'), ('fprintf','//fprintf')]` will work fine – dragon2fly Jan 29 '15 at 05:54
@KyleBooth Tried with round one but again error `SyntaxError: invalid syntax`. – Jayesh Bhoi Jan 29 '15 at 05:54
@dragon2fly Have tried like `replacements = [('printf','//printf'), ('fprintf','//fprintf')]` but again error like `AttributeError: 'list' object has no attribute 'iteritems'` – Jayesh Bhoi Jan 29 '15 at 05:57
@Jayesh you dont need `replacements.iteritems()`, just `replacements` is enough. – dragon2fly Jan 29 '15 at 06:00
@dragon2fly Error gone but now `fprintf` become `f//printf`. – Jayesh Bhoi Jan 29 '15 at 06:02
@Jayesh you need to put the `fprintf` replacement as the first tuple in the list like so: `[ ('fprintf','//fprintf'), ('printf','//printf')]` – Kyle Coventry Jan 29 '15 at 06:03
@KyleBooth No. not working..it become `fprintf` to `//f//printf` and this is in my question :) – Jayesh Bhoi Jan 29 '15 at 06:06

score 0 · Answer 4 · answered Jan 29 '15 at 06:03

(?=\bprintf\b|\bfprintf\b)

Use re.sub from re module.See demo.

https://regex101.com/r/pM9yO9/18

import re
p = re.compile(r'(?=\bprintf\b|\bfprintf\b)', re.IGNORECASE | re.MULTILINE)
test_str = "printf(\"\nReboot not supported. Exiting instead.\n\");\nfprintf(stderr, \"FATAL: operation not supported!\n\");"
subst = "//"

result = re.sub(p, subst, test_str)

Pass your file line by line and print output to different file.

Replace exact match word with specific string in python

4 Answers4