#Calculating mode of a column
df['column_name'].mode() 
#NB: This will show the index and value. To show only the value:
df['column_name'].mode()[0]

#Calculating mode of an entire dataframe or more than one series
df.mode()

#These arguments can be parsed:
df.mode(axis=0, numeric_only=False, dropna=True)
axis # axis=0 for rows and axis=1 for columns
numeric_only # False considers all values and; =True ignores all non-numerics.
dropna # =False considers all NaN values and; =True ignores all NaN values.