Question: Does anyone meet this similar FutureWarning? I got this when I was using Tiingo+pandas_datareader? The warning is like: python3.8/site-packages/pandas_datareader/tiingo.py:234: FutureWarning: In a future version of pandas all arguments of concat except for the argument 'objs' will be keyword-only return pd.concat(dfs, self._concat_axis)  I think this warning does not impact my accessing to pandas data(in my case, I fetch from tiingo api), I can get all the data I want with no problem. I just want to understand if there is any risk with my current enviroment: my python3 - 3.8.5, Python 3.8.5, pytest-6.2.4, py-1.10.0, pluggy-0.13.1 pandas_datareader version - 0.10.0 pandas version - 1.3.2  I then tested my code with a 'futureVersion' of python: 3.9.6 (comparing with python 3.8.5). To my suprise, I no longer get any warning or error, everything works fine: bellow are details updated platform win32 - Python 3.9.6, pytest-6.2.4, py-1.10.0, pluggy-0.13.1  Any advice is appreciated.

Answer: Most function parameters in python are "positional or keyword" arguments. I.e. if I have this function: def do_something(x, y): pass  Then I can either call it like this, using positional arguments: do_something(1, 2)  Or like this, using keyword arguments: do_something(x=1, y=2)  Or like this, using a mixture of the two (but note that you're not allowed to have a positional argument after a keyword argument): do_something(1, y=2)   But you can also define functions with positional-only or keyword-only parameters Say I have this other function: def do_something_else(x, /, y, *, z): pass  In this function, I've marked x as being positional-only, because it comes before the /. And I've marked z as being keyword-only, because it comes after the *. y is a positional-or-keyword parameter, as it comes after the / but before the *. This means that these two attempts to call the function will fail: the first one because z is being called as a positional argument, and the second because x is being called as a keyword argument: do_something_else(1, 2, 3) # will fail! do_something_else(x=1, y=2, z=3) # will fail!  These two attempts, however, will both succeed — y is still a positional-or-keyword parameter. do_something_else(1, 2, z=3) # fine do_something_else(1, y=2, z=3) # fine  The `FutureWarning` message. The FutureWarning message has nothing to do with the version of python you're using, but has everything to do with the version of pandas that you're using. Pandas is a third-party library, not a part of the python core, so the pandas version you're using is a completely different thing to the python version you're using. The warning is letting you know that currently, you're fine to write pd.concat(dfs, self._concat_axis), but that they're planning on changing the definition of the function in a future version of pandas so that all arguments except for objs will be keyword-only. I.e., after they make this change, pd.concat(dfs, self._concat_axis) will raise an error, and you will have to write pd.concat(dfs, axis=self._concat_axis) instead. They are most likely considering making this change because calling functions with keyword arguments is often clearer and more readable for other people.