How to check for nan and empty string

Question

I am trying to find all NaNs and empty strings (i.e "") in a Python list of strings. Please see the following code with 3 options:

names=['Pat','Sam', np.nan, 'Tom', '']
for idx,name in enumerate(names):
    if name=='':        #Option 1 
    if pd.isnull(name): #Option 2
    if np.isnan(name):  #Option 3 
        print(idx)

• Option 1: This check, name=="", doesn't catch NaN

• Option 2: This check, pd.isnull(name) doesn't catch the empty string

• Option 3: This check, np.isnan(name) gives the following error on the strings (e.g "Pat"):

----> 6 if np.isnan(name): TypeError: ufunc 'isnan' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe*''*

Question: Is there any function/method that can check for empty strings, NaNs and does not give an error when it encounters a string?

Answer 1

There is a way to combine options #1 and #2 and get the result you are looking for:

names = ['Pat', 'Sam', np.nan, 'Tom', '']
for idx, name in enumerate(names):
    if not name or pd.isnull(name):
        print(idx)

Answer 2

Just use both:

>>> names=['Pat','Sam', np.nan, 'Tom', '']
>>> for idx,name in enumerate(names):
...     if name == '' or pd.isnull(name):
...         print(idx)
...
2
4

However, realize that:

>>> pd.isnull(None)
True

So if you want to check specifically for NaN and not None, use math.isnan (while guarding against passing non-float values to math.isnan:

>>> import math
>>> for idx,name in enumerate(names):
...     if name == '' or (isinstance(name, float) and  math.isnan(name)):
...         print(idx)
...
2
4