RegEx: replace multiple values in text-CodePudding

I have a text file where each line contains specific values. They change often. I’d like to replace two values on a single line in one go without rewriting the entire line.


Current regex pattern:
(\(Psig\)- )(\d \.\d )

Regex to do one value at a time:
^(.*?(.*?\(Psig\)- ){1})(\d \.\d )

Using \1 backreference to change values

Line from file:

RPM- 1400, (Psig)- 57.66, Ts- 48.11, (Psig)- 299.33

I currently want to change the values that follows (Psig)- , currently pattern both values that I need to change but when using back reference it changes both values to same thing.

In this example:

57.66-> 22.77

299.33-> 355.26

I was thinking to use re.sub() to replace these values. Is this possible to do with this method or is there another option to do this?

CodePudding user response：

Assuming there are only two matches in the line, would you please try the following:

#!/usr/bin/python

import re

s = 'RPM- 1400, (Psig)- 57.66, Ts- 48.11, (Psig)- 299.33'
newval = ['22.77', '355.26']            # array of new values
val_iter = iter(newval)                 # iterator to return each new value

s = re.sub(r'(?<=\(Psig\)- )[\d.] ', lambda x: next(val_iter), s)
print(s)

Output:

RPM- 1400, (Psig)- 22.77, Ts- 48.11, (Psig)- 355.26

The regex (?<=\(Psig\)- )[\d.] matches a decimal value preceded by the string (Psig)- . Each time the regex matches, the value is replaced with the output of the iterator.