Getting nan using row function. However while comparing row with nan, condition is getting False

Question

This is the output of half expression mentioned in the last:

row['dep']
Out[302]: nan

However I am not getting BU in the cell 17,5.

if row['dep'] == 'nan':
     local.Cells(17,5).Value = "BU"

Can anyone please help

Answer 1

When you say 'nan' in your code, you are creating a string containing the letters 'n', 'a' and 'n'. The semantic value nan is not represented as a string in Python. You can get nan as float('nan').

Since nan is a special value and not a number (that's what NaN literally stands for, by the way), you cannot use == for comparison.

>>> float('nan') == float('nan')

will return False.

For checking if a variable is nan, it is best to use math.isnan.

Answer 2

By definition, NaN fails any value comparison. The operation == NaN will return False regardless of what's on the left side. NaN == NaN is False.

Instead, use the provided operator for this very purpose:

if isnan(row['dep']):
     local.Cells(17,5).Value = "BU"

Answer 3

Your if statement evaluates to False hence further part is not executed. This is because nan == nan evaluates to False as nan (not a number) is not defined and you cannot compare things which are not defined. Try changing your logic or using isna(), fillna() function.