sub function from re module in python

Question

sub function from re module has a input named count. Please somebody say what this input do.
re.sub(pattern, old_value, string, count)

Answer 1

"The optional argument count is the maximum number of pattern occurrences to be replaced; count must be a non-negative integer. If omitted or zero, all occurrences will be replaced".

https://docs.python.org/3.7/library/re.html#re.sub

Answer 2

Thank you

Answer 3

Python doc is very useful