Replace strings surrounded by quotation marks by underscores of the same length-CodePudding

I am writing a python script in which I need to replace strings surrounded by quotation marks into underscores, and the number of underscores should be equal to the length of strings. Here is what I have tried:

>>> re.sub(r'"(. ?)"', (len(r"\1") * "_"), '"hellohello"')
'__'

Apparently, I have got something wrong there. The expected outcome for the test above would be 10 underscores but I got two. Any ideas where it went wrong?

[EDIT] I think r"\1" back references to the first match because

>>> re.sub(r'"(. ?)"', r"\1"  "pp", '"hellohello"')
'hellohellopp'

CodePudding user response：

Using re.sub with a callback function works nicely here:

inp = '"hellohello"'
output = re.sub(r'"(.*?)"', lambda m: '"'   re.sub(r'.', '_', m.group(1))   '"', inp)
print(output)  # "__________"

The trick here is to match "...", while capturing the quoted content in the first capture group. We then replace each character of content with a single underscore.