Question

Say, I want to change the string ‘A = (x+2.)*(y+3.)-1‘

to

‘A = (x+2.0e0)*(y+3.0e0)-1.0e0‘.

Every number like 2. or just 2 should be changed. How to do this?

Thanks a lot!

Answer 1

Given the comment you wrote, this kind of regular expression should work:

import re

str = 'A = (x+2.)*(y+3.)-1'
print re.sub(r'(\d+)\.?',r'\1.0e0',str)

Output:

A = (x+2.0e0)*(y+3.0e0)-1.0e0

Explanation of regexp:

• (...) – means capturing group, what you need to capture to reuse during replacement
• \d – means any number, equivalent to [0-9]
• + – means 1 or more occurance, equivalent to {1,}
• \.? – means that we want either 0 or 1 dot. ? is equivalent to {0,1}

In replacement:

• \1 – means that we want to take first captured group and insert it here