replace some values in column pandas with null code example

Example 1: how to replace nan with 0 in pandas

df['product']=df['product'].fillna(0)
df['context']=df['context'].fillna(0)
df

Example 2: replace "-" for nan in dataframe

df.replace(np.nan,0)

Example 3: fillna string

# importing pandas module 
import pandas as pd 
  
# making data frame from csv file 
nba = pd.read_csv("nba.csv") 
  
# replacing na values in college with No college 
nba["College"].fillna( method ='ffill', inplace = True)