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         


        

Answer 1

Idea is create new DataFrame filled by styles by condition with Styler.apply, for set rows by conditions is used numpy.where:

def expired(x):
    c1 = 'background-color: red'
    c2 = 'background-color: green'

    df1 = pd.DataFrame('', index=x.index, columns=x.columns)
    m = x['Expiration Date'] < today
    df1['Expiration Date'] = np.where(m, c1, c2)
    return df1

df.style.apply(expired, axis=None)

If coloring all rows by condition use DataFrame.mask:

def expired(x):
    c1 = 'background-color: red'
    c2 = 'background-color: green'

    df1 = pd.DataFrame(c1, index=x.index, columns=x.columns)
    m = x['Expiration Date'] < today
    df1 = df1.mask(m, c2)
    return df1

Answer 2

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)