Python Basics: How To Check If A Function Returns Mutiple Values?

July 24, 2024 Post a Comment

Basic stuff I know...;-P But what is the best way to check if a function returns some values? def hillupillu(): a= None b='lillestalle' return a,b if i and j in hil

Solution 1:

If you meant that you can't predict the number of return values of some function, then

i, j = hillupillu()

will raise a ValueError if the function doesn't return exactly two values. You can catch that with the usual try construct:

try:
    i, j = hillupillu()
except ValueError:
    print("Hey, I was expecting two values!")

This follows the common Python idiom of "asking for forgiveness, not permission". If hillupillu might raise a ValueError itself, you'll want to do an explicit check:

r = hillupillu()
iflen(r) != 2:  # maybe check whether it's a tuple as well with isinstance(r, tuple)print("Hey, I was expecting two values!")
i, j = r

If you meant that you want to check for None in the returned values, then check for None in (i, j) in an if-clause.

Solution 2:

Functions in Python always return a single value. In particular they can return a tuple.

If you don't know how many values in a tuple you could check its length:

tuple_ = hillupillu()
i = tuple_[0] if tuple_ else None
j = tuple_[1] if len(tuple_) > 1 else None

Solution 3:

After receiving the values from the function:

i, j = hillupillu()

You can check whether a value is None with the is operator:

if i is None: ...

You can also just test the value's truth value:

if i: ...

Solution 4:

if(i == ""orj== ""):
   //execute code

something like that should wordk, but if your giving it a None value you would do this

if(i == None or j == None):
    //execute code

hope that helps

Solution 5:

You can check whether the return value of the function is a tuple:

r_value = foo(False)

x, y = None, Noneiftype(r_value) == tuple:
    x, y = r_value
else:
    x = r_value
    
print(x, y)

This example is suited for a case where the function is known to return either exactly one tuple of length 2 (for example by doing return a, b), or one single value. It could be extended to handle other cases where the function can return tuples of other lengths.

I don't believe @Fred Foo's accepted answer is correct for a few reasons:

It will happily unpack other iterables that can be unpacked into two values, such as a list or string of lengths 2. This does not correspond to a return from a function that returned multiple values.
The thrown exception can be TypeError, not a ValueError.
The variables that store the return value are scoped to the try block, and so we can only deal with them inside that block.
It doesn't show how to handle the case where there is a single returned value.

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