CODEWITHSUNDEEP
pythonfilepython-2.6
Mika H.
Mika H.

Reputation: 4329

Reading and writing to files in the same iteration

Suppose I have a list of files, and I want to iterate over it, for each one reading its content, sending the content to a function processContent(), and writing the whole thing back into the file. Would the following code be an appropriate way to do it?

for curfile in files:
    with open(curfile, 'r+') as infile
        content = infile.read()
        processed_content = processContent(content)
        infile.write(processed_content)

In other words, reading and writing in the same iteration.

Upvotes: 0

Views: 215

Answers (1)

Ashwini Chaudhary
Ashwini Chaudhary

Reputation: 250951

for curfile in files:
    with open(curfile, 'r+') as infile:
        content = infile.read()
        processed_content = processContent(content)
        infile.truncate(0)   # truncate the file to 0 bytes
        infile.seek(0)       # move the pointer to the start of the file
        infile.write(processed_content)

Or use a temporary file to write the new content and then rename it back to the original file:

import os
for curfile in files:
    with open(curfile) as infile:
        with open("temp_file", 'w') as outfile:
            content = infile.read()
            processed_content = processContent(content)
            outfile.write(processed_content)
    os.remove(curfile) # For windows only
    os.rename("temp_file", curfile)

If you want to process one line at once then try fileinput module

Upvotes: 4

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