What is the difference between .replace and re.sub?

Question

Are they the same? Why would I use re.sub after import the module, and not just use "Something".replace?
For example:
What is the difference between .replace re.sub?
import re

str = "My name is David. Hi David."
pattern = r"David"
newstr = re.sub(pattern, "Amy", str)
print(newstr)

================================

newstr2 = str.replace("David", "Amy")
print (newstr2)

Answer 1

https://stackoverflow.com/questions/5668947/use-pythons-string-replace-vs-re-sub#5668962