On 05/12/2010 21:01, Martin v. Loewis wrote:
result = myfunction (vars)
if not result:
# error condition
Now above I first realized that the function can also return an empty
list under some conditions and so changed it to
If your function returns a list when successful, it should not return
False in the error case. Instead, it should return None (indicating that
there is no list).
Then the condition changes to
result = myfunction()
if result is None:
# error condition
Using None for "no result available" is very common in Python. Using
False for the same purpose (i.e. returning either a list or False)
is not. If you return False from a function, the only other possible
result should be True.
As an example, the re module uses both two approaches.
If you ask it to compile a regex:
rgx = re.compile(regex)
it either returns a PatternObject (if the regex is valid) or raises an
exception (if the regex isn't valid).
If you ask it to search a string:
rgx.search(string)
it returns either a MatchObject (if the match is successful) or None
(if the match isn't successful).
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