Python find and replace strings in files with argument that the string is quoted and not part of bigger string

问题

i need a solution to the following problem. I want to replace a dynamic string if found in a file but only if there are quotes surrounding the string, either next to it or with max two spaces between, and not be part of bigger string (in python) :

ori = 'testing'
rep = 'posting'

file contents:

Line1 This is one line with some words for testing purposes
Line2 this is the seconds "testing" function.
Line3 that is one more " testing" line
Line4 "testing"
Line5 "  testing"
Line6 "testing  "
Line7 "  testing  "

Im looking for the following result preferably with regex as simple and efficient way instead of a separate function.

Line1 This is one line with some words for testing purposes
Line2 this is the seconds "testing" function.
Line3 that is one more " testing" line
Line4 "posting"
Line5 "  posting"
Line6 "posting  "
Line7 "  posting  "

regex magicians may help me at this one.

Thanks in advance.

回答1:

A regular expression would be a good tool for such a task.
Always take care to express them clearly.
Regular expressions can quickly become puzzling and hard to debug.

import re

original = 'testing'
replacement = 'posting'

line1 = 'This is one line with some words for testing purposes'
line2 = 'this is the seconds "testing" function.'
line3 = 'that is one more " testing" line'
line4 = '"testing"'
line5 = '"  testing"'
line6 = '"testing  "'
line7 = '"  testing  "'

lines = [line1, line2, line3, line4, line5, line6, line7]

starts_with_parentheses = '^"'
ends_with_parentheses = '"$'
one_space = ' {1}'
two_spaces = ' {2}'
none_one_or_two_spaces = '(|{}|{})'.format(one_space, two_spaces)

query = starts_with_parentheses \
        + none_one_or_two_spaces \
        + original \
        + none_one_or_two_spaces \
        + ends_with_parentheses

for line in lines:
    match = re.search(query, line)
    if match:
        line = line.replace(original, replacement)

    print(line)

Outputs:

This is one line with some words for testing purposes
this is the seconds "testing" function.
that is one more " testing" line
"posting"
"  posting"
"posting  "
"  posting  "

来源：https://stackoverflow.com/questions/59021636/python-find-and-replace-strings-in-files-with-argument-that-the-string-is-quoted

标签

python

regex

regex-lookarounds