how to replace values with nan in pandas code example

Example 1: replace "-" for nan in dataframe

df.replace(np.nan,0)

Example 2: replacing values in pandas dataframe

df['coloum'] = df['coloum'].replace(['value_1','valu_2'],'new_value')

Example 3: how to replace zero value in python dataframe

nonzero_mean = df[ df.col != 0 ].mean()