Replace a string in one file with another string in another file

Question

I have a text file with several lines and want to replace strings that match certain values. I opted to use a dictionary to store the string-to-be-replaced as the key, and the replacement as the value. The dictionary was created by opening another text file (template.txt) that has two columns separated by a single Tab:

140101002   name44
140101030   name2
140101004   name3
140101058   name94

The input file (input.txt) has the following text:

...text... <!-- 140101002 --> ...text...
...text... <!-- 140101030 --> ...text...
...text... <!-- 140101004 --> ...text...
...text... <!-- 140101058 --> ...text...

and I want to search for the strings in the template.txt first column (like 140101002) and replace it with the strings in the second column (like name44), so that the output file (output.txt) will look like this:

...text... <!-- name44 --> ...text...
...text... <!-- name2 --> ...text...
...text... <!-- name3 --> ...text...
...text... <!-- name94 --> ...text...

I have tried fixing this several times but cannot get it to work as intended:

fhand = open("/home/Documents/input.txt")
template = open("/home/Documents/template.txt")
fout = open("/home/Documents/output.txt","w")

# store the values in the dictionary:
templateDict = dict()
for line in template:
  lineList = line.split("\t")
  templateDict[lineList[0]] = lineList[1]

# replacement:
for line in fhand:
  for key in templateDict:
    if key in line2:
      line2 = line2.replace(key,templateDict[key])
  fout.write(line2) # write to output.txt

fout.close()

Is there any error you are getting ? Also i notice in the replacement loop, it should be line instead of line2 — navinkb
– navinkb, Commented Oct 17, 2018 at 3:58

Ajax1234 · Accepted Answer · 2018-10-17 03:58:05Z

2

You can read the first file into a dictionary, and then use re.sub:

import re
d = dict(re.split('\s+', i.strip('\n')) for i in open('filename.txt'))
content = [i.strip('\n') for i in open('filename2.txt')]
with open('results.txt', 'w') as f:
  f.write('\n'.join(re.sub('(?<=\<\!\-\-\s)\d+(?=\s\-\-\>)', lambda x:d[x.group()], i) for i in content))

Output:

...text... <!-- name44 --> ...text...
...text... <!-- name2 --> ...text...
...text... <!-- name3 --> ...text...
...text... <!-- name94 --> ...text...

answered Oct 17, 2018 at 3:58

Ajax1234

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JAT86 · Accepted Answer · 2018-10-17 04:35:38Z

1

I had to strip the newline character before splitting the line into a list.

fhand = open("/home/Documents/input.txt")
template = open("/home/Documents/template.txt")
fout = open("/home/Documents/output.txt","w")

# store the values in the dictionary:
templateDict = dict()
for line in template:
  lineList = line.strip("\n").split("\t")
  templateDict[lineList[0]] = lineList[1]

# replacement:
for line in fhand:
  for key in templateDict:
    if key in line:
      line = line.replace(key,templateDict[key])
  fout.write(line) # write to output.txt

fout.close()

answered Oct 17, 2018 at 4:35

JAT86

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