What does S.find(sub[, start[, end]]) mean?

I'm learning to use python docstring.

>>> print(str.find.__doc__)
S.find(sub[, start[, end]]) -> int
...

When I print str.find() docstring, I don't understand what this means.

Solution

It means that the method find in String will take in 3 parameters of which 2 are optional.

Example:

 a = "Hello World"
 a.find("World")        # returns 6
 a.find("World", 4)     # returns 6
 a.find("World", 4, 6)  # returns -1 meaning it cannot be found

Back to your output:

S.find(sub[, start[, end]]) -> int

S here refers to the String variable which in my case was a.
-> int means the function outputs an integer which is by default the position of the found word or -1 if not found which in my case was 6 and -1.
sub refers to the word you are looking for which in my case was "World".
start and end refer to the start and end indices as to where to find the string which in my case was 4 and 6 respectively.