Using "and" and "or" operator with Python strings -

i don't understand meaning of line:

parameter , (" " + parameter) or ""

where parameter string

why 1 want use and , or operator, in general, python strings?

suppose using value of parameter, if value none, rather have empty string "" instead of none. in general?

if parameter:     # use parameter (well expression using `" " + parameter` in case else:     # use ""

this expression doing. first should understand and , or operator does:

so, expression:

parameter , (" " + parameter) or ""

which equivalent to:

(parameter , (" " + parameter)) or  "" #    a1               a2               b #                               or   b

how expression evaluated if:

parameter - a1 evaluated true:

result = (true , " " + parameter) or ""  result = (" " + parameter) or ""  result = " " + parameter

parameter - a1 none:

result = (none , " " + parameter) or ""  result = none or ""  result = ""

as general suggestion, it's better , more readable use a if c else b form expression conditional expression. so, should better use:

" " + parameter if parameter else ""

instead of given expression. see pep 308 - conditional expression motivation behind if-else expression.

Bradly