Write a program that reads characters from the keyboard one by one. All lower case characters get stored inside the file LOWER, all upper case characters get stored inside the file UPPER and all other characters get stored inside file OTHERS.

lower_file = open("LOWER.txt", 'w')
upper_file = open("UPPER.txt", 'w')
others_file = open("OTHERS.txt", 'w')
ans = 'y'
while ans == 'y':
    char = input("Enter a character: ")
    if char.islower():
        lower_file.write(char + "\n")
    elif char.isupper():
        upper_file.write(char + "\n")
    else:
        others_file.write(char + "\n")
    ans = input("Want to enter a character? (y/n): ")
lower_file.close()
upper_file.close()
others_file.close()

Output

Enter a character: e
Want to enter a character? (y/n): y
Enter a character: A
Want to enter a character? (y/n): y
Enter a character: D
Want to enter a character? (y/n): y
Enter a character: c
Want to enter a character? (y/n): y
Enter a character: 7
Want to enter a character? (y/n): y
Enter a character: @
Want to enter a character? (y/n): n

The file "LOWER.txt" includes:

e
c

The file "UPPER.txt" includes:

A
D

The file "OTHERS.txt" includes:

7
@