python - Highlight cell on condition

Question

I'm trying to highlight all cells that are before the current date. However I am highlighting all cells instead of just the old dates.

import pandas as pd
from datetime import datetime 

#get file 
df = pd.read_excel(r'C:Userscc-621.xlsx')
df

# sort the data by date 
df['Date'] = pd.to_datetime(df['Expiration Date'])
df = df.sort_values(by='Expiration Date')
df = df.reset_index()
df

# sort by todays date 
today = datetime.now(tz=None)
today

def expired(self):
    for index, rows in df.iterrows():
        color = 'red' if rows['Expiration Date'] < today else 'green'
        return 'background-color: %s' %color

new = df.style.applymap(expired)
new

Answer 1

applymap is executed on each cell. You don't need to loop over each row if using this. However, it seems you are trying to highlight the entire row, so you likely want apply by row. Using this method, you have to return an array with the same size as each row.

def expired(val):
    return ['background-color: green' if val['Expiration Date'] else ''] * len(val)

new = df.style.apply(expired, axis=1)