Testing if a pandas DataFrame exists

Question

In my code, I have several variables which can either contain a pandas DataFrame or nothing at all. Let\'s say I want to test and see if a certain DataFrame has been created ye

Answer 1

In my code, I have several variables which can either contain a pandas DataFrame or nothing at all

The Pythonic way of indicating "nothing" is via None, and for checking "not nothing" via

if df1 is not None:
    ...

I am not sure how critical time is here, but since you measured things:

In [82]: t = timeit.Timer('if x is not None: pass', setup='x=None')

In [83]: t.timeit()
Out[83]: 0.022536039352416992

In [84]: t = timeit.Timer('if isinstance(x, type(None)): pass', setup='x=None')

In [85]: t.timeit()
Out[85]: 0.11571192741394043

So checking that something is not None, is also faster than the isinstance alternative.