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Highlight the negative values red and positive values black in Pandas Dataframe
  • Last Updated : 20 Aug, 2020
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Let’s see various methods to Highlight the positive values red and negative values black in Pandas Dataframe.
First, Let’s make a Dataframe:

Python3




# Import Required Libraries
import pandas as pd
import numpy as np
  
  
# Create a dictionary for the dataframe
dict = {
  'Name': ['Sukritin', 'Sumit Tyagi'
           'Akriti Goel', 'Sanskriti',
           'Abhishek Jain'],
   'Age': [22, 20, 45, 21, 22],
  'Marks': [90, 84, -33, -87, 82]
}
  
# Converting Dictionary to
# Pandas Dataframe
df = pd.DataFrame(dict)
  
# Print Dataframe
print(df)

Output: 

Now, come to the highlighting part. Our objective is to highlight negative values red and positive values black.



Method 1: Using Dataframe.style.apply().

Syntax: DataFrame.style.apply(self, func, axis=0, subset=None, **kwargs)
Parameters: 

  • func: It should take a pandas.Series or pandas.DataFrame based on the axis and should return an object with the same shape. 
  • axis: {0 or ‘index’, 1 or ‘columns’, None}, default 0. Apply to each column (axis=0 or ‘index’), to each row (axis=1 or ‘columns’), or to the entire DataFrame at once with axis=None. 
  • subset: Set of columns or rows on which you want to call the func. 
  • **kwargs: Pass along to func.

Returns: Styler object.

Example 1: Highlighting text.

Python3




# Define a function for colouring 
# negative values red and 
# positive values black
def highlight_max(s):
    if s.dtype == np.object:
        is_neg = [False for _ in range(s.shape[0])]
    else:
        is_neg = s < 0
    return ['color: red;' if cell else 'color:black' 
            for cell in is_neg]
  
# Using apply method of style 
# attribute of Pandas DataFrame
df.style.apply(highlight_max)

Output: 

 



Example 2: Highlighting cells instead of text.

Python3




# Define a function which 
# returns the list for 
# df.style.apply() method
def highlight_max(s):
    if s.dtype == np.object:
        is_neg = [False for _ in range(s.shape[0])]
    else:
        is_neg = s < 0
    return ['background: red; color:white' 
            if cell else 'background:black; color:white' 
            for cell in is_neg]
  
# Using apply method of style 
# attribute of Pandas DataFrame
df.style.apply(highlight_max)

Output: 

 

Method 2: Using dataframe.style.applymap() method.

Syntax: DataFrame.style.applymap(self, func, subset=None, **kwargs)
Parameters: 

  • func: It takes a scalar value and return the scalar values 
  • subset: Set of columns or rows on which you want to call the func. 
  • **kwargs: Pass along to func.

Returns: Styler object.

Example 1: Highlighting text.

Python3




# Define a function for 
# colouring negative values 
# red and positive values black
def highlight_max(cell):
    if type(cell) != str and cell < 0 :
        return 'color: red'
    else:
        return 'color: black'
  
df.style.applymap(highlight_max)

Output: 

 

Example 2: Highlighting cells instead of text.

Python3




# Define a function which 
# returns string for 
# applymap() method
def highlight_max(cell):
    if type(cell) != str and cell < 0 :
        return 'background: red; color:black'
    else:
        return 'background: black; color: white'
  
df.style.applymap(highlight_max)

Output: 

 Note: pandas.DataFrame.applymap() method passes only single cell into the callable function while the pandas.DataFrame.apply() passes the pandas.Series to the callable function.

Reference: Styling in Pandas
 

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