Python script for delete NaN by null value

Question

I try to delete NaN value in pyhton, it’s ok but I have one issue in my table in Knime flow :

df = pd.read_excel(filename, sheet_name="LAB", usecols = 'A:AB')#, headers=True)


df2 = df.replace(np.nan, '', regex=True)

output_table = df

Issue consol : ERROR Python Script (1⇒1) 3:1720 Execute failed: More than one type in column MASTER_REORG_ID. Found float and str

It’s possible to help me ? Thanks !