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POFastest way to compare and replace key value pairs in Python
 

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  1. POFastest way to compare and replace key value pairs in Python
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    <p>I have a number of files where I want to replace all instances of a specific string with another one.</p> <p>I currently have this code:</p> <pre><code> mappings = {'original-1': 'replace-1', 'original-2': 'replace-2'} # Open file for substitution replaceFile = open('file', 'r+') # read in all the lines lines = replaceFile.readlines() # seek to the start of the file and truncate # (this is cause i want to do an "inline" replace replaceFile.seek(0) replaceFile.truncate() # Loop through each line from file for line in lines: # Loop through each Key in the mappings dict for i in mappings.keys(): # if the key appears in the line if i in line: # do replacement line = line.replace(i, mappings[i]) # Write the line to the file and move to next line replaceFile.write(line) </code></pre> <p>This works ok, but it is very slow for the size of the mappings and the size of the files I am dealing with.</p> <p>For instance, in the "mappings" dict there are 60728 key value pairs. I need to process up to 50 files and replace all instances of "key" with the corresponding value, and each of the 50 files is approximately 250000 lines.</p> <p>There are also multiple instances where there are multiple keys that need to be replaced on the one line, hence I cant just find the first match and then move on.</p> <p>So my question is:</p> <p>Is there a faster way to do the above? I have thought about using a regex, but I am not sure how to craft one that will do multiple in-line replaces using key/value pairs from a dict.</p> <p>If you need more info, let me know.</p>
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    1. USHurgh
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    1. COThe linked duplicate question has answers that cannot be topped.
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      1. POFastest way to compare and replace key value pairs in Python
      1. USJoe Frambach
    2. COThe linked question has a *much* smaller dictionary of replacements. Given the questions are about performance, I'm baffled by the idea that this difference doesn't distinguish the questions.
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      1. POFastest way to compare and replace key value pairs in Python
      1. USSteve Jessop
    3. COIt will go a lot faster if you don't do it a line at a time. Since you can read the whole file into memory, just do that and do one replace for each term.
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      1. POFastest way to compare and replace key value pairs in Python
      1. USkindall
 

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