Question

I am using a 3rd party library function which reads a set of keywords from a file, and is supposed to return a tuple of values. It does this correctly as long as there are at least two keywords. However, in the case where there is only one keyword, it returns a raw string, not a tuple of size one. This is particularly pernicious because when I try to do something like

for keyword in library.get_keywords():
    # Do something with keyword

, in the case of the single keyword, the for iterates over each character of the string in succession, which throws no exception, at run-time or otherwise, but is nevertheless completely useless to me.

My question is two-fold:

Clearly this is a bug in the library, which is out of my control. How can I best work around it?

Secondly, in general, if I am writing a function that returns a tuple, what is the best practice for ensuring tuples with one element are correctly generated? For example, if I have

def tuple_maker(values):
    my_tuple = (values)
    return my_tuple

for val in tuple_maker("a string"):
    print "Value was", val

for val in tuple_maker(["str1", "str2", "str3"]):
    print "Value was", val

I get

Value was a
Value was  
Value was s
Value was t
Value was r
Value was i
Value was n
Value was g
Value was str1
Value was str2
Value was str3

What is the best way to modify the function my_tuple to actually return a tuple when there is only a single element? Do I explicitly need to check whether the size is 1, and create the tuple seperately, using the (value,) syntax? This implies that any function that has the possibility of returning a single-valued tuple must do this, which seems hacky and repetitive.

Is there some elegant general solution to this problem?

Answer 1

You need to somehow test for the type, if it’s a string or a tuple. I’d do it like this:

keywords = library.get_keywords()
if not isinstance(keywords, tuple):
    keywords = (keywords,) # Note the comma
for keyword in keywords:
    do_your_thang(keyword)