Issue with shading in Venn Diagram

Question

I am using the matplotlib_venn library for creating the Venn diagram, and the shading issue seems to appear whenever I try to evaluate a complement of a set or expression.

My code:

import matplotlib.pyplot as plt
from itertools import product
from matplotlib_venn import venn3, venn3_circles

#Initialize
universal_set = set()
empty_set = set()
complement = set()
expression = ""
setA = set()   
setB = set() 
setC = set()

def evaluate_expression(formula, empty_set):
    for x in product([False, True], repeat=3):
        x_dict = dict(zip('xyz', x))
        x_dict['universal_set'] = universal_set
        x_dict['empty_set'] = empty_set
        x_dict['complement'] = complement

        if 'empty_set' in formula:
            formula = formula.replace('empty_set', 'False')
        if 'universal_set' in formula:
            formula = formula.replace('universal_set', 'True')
        if 'complement' in formula:
            formula = formula.replace('complement', 'True')

        if eval(formula, {}, x_dict):
            yield ''.join(str(int(x_i)) for x_i in x)

def plot_diagram(formula, empty_set):
    plt.figure(figsize=(6, 6))
    v = venn3(subsets=[1] * 7,
              set_colors=['white'] * 3,
              subset_label_formatter=lambda x: '')

    for region in evaluate_expression(formula, empty_set):
        if region != '000':
            v.get_patch_by_id(region).set_color('#FFC0CB')
        else:
            ax= plt.axes()
            ax.figure.set_facecolor('#FFC0CB')

    # Add labels for setA, setB, and setC
    v.get_label_by_id('100').set_text(', '.join(map(str, setA - setB - setC)))
    v.get_label_by_id('010').set_text(', '.join(map(str, setB - setA - setC)))
    v.get_label_by_id('001').set_text(', '.join(map(str, setC - setB - setA)))

    # Add labels for intersections
    v.get_label_by_id('101').set_text(', '.join(map(str, setA & setC - setB)))
    v.get_label_by_id('110').set_text(', '.join(map(str, setA & setB - setC)))
    v.get_label_by_id('011').set_text(', '.join(map(str, setB & setC - setA)))
    v.get_label_by_id('111').set_text(', '.join(map(str, setB & setC & setA)))

    venn3_circles(subsets=[1] * 7, linestyle='solid')


#Create menu
def menu():
    print("#1 Enter a number to Set A")
    print("#2 Enter a number to Set B")
    print("#3 Enter a number to Set C")
    print("#4 Evaluate Expression")
    print("#5 Display the Venn Diagram")
    print("#6 Exit") 

#Execute depending on user's choice
while True:
    menu ()
    choice= input("Enter your number of choice: ")

    if choice == '1':
        try:
            setA.update(map(int, input("Enter a number to set A (separate using space): ").split()))
        except ValueError: 
            print("Error. Input must be an integer")
    elif choice == '2':
        try:
            setB.update(map(int, input("Enter a number to set B (separate using space): ").split()))
        except ValueError: 
            print("Error. Input must be an integer ")
    elif choice == '3':
        try:
            setC.update(map(int, input("Enter a number to set C (separate using space): ").split()))
        except ValueError: 
            print("Error. Input must be an integer")
    elif choice == '4': 
        print("x for set A, y for set B, z for set C") 
        print("| for union, & for intersection, -complement for complement, universal_set for universal set, empty_set for empty set")
        expression = input("Evaluate Expression: ")
        

    elif choice == '5':
        if expression:
            try:
                plot_diagram(expression, empty_set)
                plt.show()
            except Exception as e:
                print("Invalid formula. Error:", str(e))
        else:
            print("Please evaluate an expression first.")
    elif choice =='6':
        print("Exiting the program.")
        break
    else:
        print("Invalid input")

I would appreciate any guidance or suggestions on how to ensure that the unshaded parts are consistently displayed in a pure white color.

here's an example of an expression and its output: x-complement

I have attempted to adjust the colors in the Venn diagram, specifically in the plot_diagram function, but I haven't been successful in making the unshaded parts completely white.

Answer 1

Just add alpha=1.0 to your venn3 function call.

By default venn3 generates regions with some transparency (alpha=0.4) which is what makes the pink background partially visible through the white regions.