NaN-8.py

In [59]:
print('Data types:\n', new_df.dtypes)

# (Although such an assignment is not correct, but the purpose here is to
# demonstrate use of mean/median/mode academically so let's continue with it)
new_df.loc['i2', 'c3'] = 10

new_df['c3'] = new_df['c3'].astype('float64') # if skipped a warning would be thrown 
                                              # as '#$%' was a string.
    
print('\n Data types(after):\n', new_df.dtypes)

Out [59]:
Data types:
 c0    float64
c1    float64
c2    float64
c3     object
dtype: object

 Data types(after):
 c0    float64
c1    float64
c2    float64
c3    float64
dtype: object