Right-to-left string replace in Python?

Question

I want to do a string replace in Python, but only do the first instance going from right to left. In an ideal world I\'d have:

myStr = \"mississippi\"
print          


        

Answer 1

>>> re.sub(r'(.*)iss',r'\1XXX',myStr)
'missXXXippi'

The regex engine cosumes all the string and then starts backtracking untill iss is found. Then it replaces the found string with the needed pattern.

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Some speed tests

The solution with [::-1] turns out to be faster.

The solution with re was only faster for long strings (longer than 1 million symbols).