Python-用正则表达式中的字符串替换字符串EXCEPT的所有实例

Question

I would like to replace all mentions of the string "camel" except when it occurs in the context of the below in bold:

Source{[Name="Camel"]} 

In that case I would like to leave it as is. I have a regex which can identify this format:

Source{\[Name=\"(\w+)\"\]}

So for example:

let
    Source=#"Middle East",
    Camel = Source{[Name="Camel"]}[Content],
    #"Invoke Custom Function1" = Table.AddColumn(Camel)
    #"Removed Other Columns1" = Table.SelectColumns(#"Invoke Custom 
    Function1", {"Camel"})

should be changed to:

let
        Source=#"Middle East",
        Dog = Source{[Name="Camel"]}[Content],
        #"Invoke Custom Function1" = Table.AddColumn(Dog)
        #"Removed Other Columns1" = Table.SelectColumns(#"Invoke Custom 
        Function1", {"Dog"})

Answer 1

steps:

1. Replace all occurrences of camel to dog
2. Replace all occurrences of source{[name="dog"]} to source{[name="camel"]}

inefficient but will do the trick

Answer 2

You may use

re.sub(r'(Source{\[Name="\w+"]})|\bCamel\b', lambda x: x.group(1) or 'Dog', text)

See the Python demo

Details

• (Source{\\[Name="\\w+"]})|\\bCamel\\b - matches and captures into Group 1 the pattern you have ( Source{[Name="some_word123"}} like string) or will match a Camel whole word
• lambda x: x.group(1) or 'Dog' callable will put back the text in Group 1 if Group 1 matched, else, the word Camel will be replaced with Dog .

Answer 3

The key insight here is that no part of the string can match twice. So if Source{[Name="Camel"]} matches, Camel inside it can't match. So we make regexp an alternation, and check if we matched the part that we wanted to replace, otherwise we just return what we found, unchanged:

import re
camel_re = re.compile(r"Source\{\[Name=\"Camel\"\]\}|(?P<replacee>Camel)")

def camel_replacer(m):
    if m.group('replacee'):
        return "Dog"
    else:
        return m.group()

camel_re.sub(camel_replacer, text)