如何使用python脚本用字典键值替换文件中的字符串值

Question

How can I replace a string in file with dictionary value using python:

I have a file with content as below:

No.of documents inserted in collection{col_id="feed-496"} 580
No.of documents inserted in collection{col_id="feed-497"} 620
No.of documents inserted in collection{col_id="feed-498"} 630

Now I have a dictionary as below:

dict1={'feed-496':'high','feed-497':'low','feed-498':'medium'}

How can I replace 'feed-496' in file with key value from above dictionary using python script.

Answer 1

Approach with built-ins:

# file_contents = file.read() or similar, as long as it's a string.

for find, replacement in dict1.items():
    file_contents.replace(find, replacement)

Note that replacements in this case should never have also appear in the dictionary keys or they will end up being replaced by later iterations of the loop.

Alternatively, with regex:

import re

# ...

# Make a function that picks what to replace with.
def feed_level(match_obj):
    # Use the capture group (see regex below) as key for the dictionary.
    return dict1[match_obj.group(0)]

re.sub(r'col_id="(.*?)"', feed_level, file_contents)

This does not have the same limitation as the other approach above. Both possibilities allow you to expand the dictionary at any time without having to modify this code when you do it.

Answer 2

To replace certain strings in a text file use .replace(wrongelement, rightelement)

in.txt:

Hello and welcome to pyton.

Code:

fin = open("in.txt", "rt")
fout = open("out.txt", "wt")

for line in fin:
    fout.write(line.replace('pyton', 'python'))

fin.close()
fout.close()

out.txt:

Hello and welcome to python.

Your code would then look something like this:

dict1={'feed-496':'high','feed-497':'low','feed-498':'medium'}
fin = open("in.txt", "rt")
fout = open("out.txt", "wt")

for line in fin:
    for key in dict1:
        fout.write(line.replace(key, dict1[key]))

fin.close()
fout.close()

Answer 3

Using Regex.

Ex:

import re

dict1={'feed-496':'high','feed-497':'low','feed-498':'medium'}

with open(filename) as infile:
    for line in infile:                         #Iterate Each Line
        key = re.search(r'\"(.*?)\"', line)     #Search for key between Quotes
        if key:
            print(line.replace(key.group(1), dict1.get(key.group(1), key.group(1))))    #Replace Value