python-regexHow to replace in a file using Python regex?

Regex (Regular Expressions) can be used to replace text in a file using Python.

import re

# open the file
f = open('file.txt', 'r')

# read the file
text = f.read()

# close the file
f.close()

# replace the text
text = re.sub('old_text', 'new_text', text)

# open the file
f = open('file.txt', 'w')

# write the new text
f.write(text)

# close the file
f.close()

The example code above will open a file, read the contents, replace the text, and write the new text back to the file.

Code explanation

1. import re - imports the regular expression module
2. f = open('file.txt', 'r') - opens the file in read mode
3. text = f.read() - reads the contents of the file
4. f.close() - closes the file
5. text = re.sub('old_text', 'new_text', text) - replaces the text using the regular expression module
6. f = open('file.txt', 'w') - opens the file in write mode
7. f.write(text) - writes the new text to the file
8. f.close() - closes the file

Helpful links

• Python Regular Expressions
• Python File I/O

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