Python regex: substitute all occurrence of a certain string NOT after a specific character

Question

How can I substitute all occurrence of a certain string NOT after a specific character in Python?

For example, I want to substitute all occurrence of abc NO

Answer 1

result = re.sub("(?

• The negative lookbehind (? asserts that what precedes is not x
• abc matches abc
• We replace with def

Reference

• Lookahead and Lookbehind Zero-Length Assertions
• Mastering Lookahead and Lookbehind