As you are not using 'i' in for loop. Change it '_' as shown in below

def main():
    print ("This program illustrates a chaotic function")
    x = (float(input("Enter a number between 0 and 1: ")))
    for _ in range(10):
        x = 3.9 * x * (1-x)
        print (x)

As you are not using 'i' in for loop. Change it '_' as shown in below

def main():
    print ("This program illustrates a chaotic function")
    x = (float(input("Enter a number between 0 and 1: ")))
    for _ in range(10):
        x = 3.9 * x * (1-x)
        print (x)

Assign unnecessary variable values to _. While _ is still a standard identifier, it's commonly used to indicate non-essential variable content for tools(i.e., VSCode in your case) and human readers, preventing warnings about its unused status.