I want to pass to a function a string argument. But a list containing one string element is ok, too.
Is there a more compact / pythonic way to to this?
files = ["myfile"]
isinstance(files[0], list) and len(files[0]) == 1
2 Answers
You can do it by
files = ["myfile"]
function(files if isinstance(files, list) and len(files) == 1 else files[0])
or you can change the files[0] to other element if you want a diffrent element in case files is not a list that contain 1 item.
Comments
I tend to use a *args parameter to avoid the check.
def f(*args):
for arg in args:
print(arg)
f('foo')
foo
f(*['foo'])
foo
Of course the caller must use the correct calling convention, which may or may not be problematic.
If the above approach is not feasible, and it also not feasible to redesign the application to avoid this argument overloading then isinstance is as good as anything.
I would check vs str so that containers other than lists are accepted by the function (such as deques and tuples).
s = files if isinstance(files, str) else files[0]
1 Comment
leonard vertighel
This is a very nice solution, but I have multiple arguments to check this way, and I cannot use
def f(*args1, *args2, *args3)
isinstance(files, list) and len(files) == 1insteadfinal_string = ' '.join(lis[0])also yourisinstance(files[0], list) and len(files[0]) == 1will result in false. the correct way can beisinstance(files[0], str) and len(files) == 1False, in yoursTrue