import secrets
import string

# 1. Define your character groups
letters = string.ascii_letters
digits = string.digits
special = "!@#$%^&"

# 2. Combine all characters for the "pool"
all_characters = letters + digits + special

# 3. Start the password with one guaranteed character from each group
password_list = [
    secrets.choice(letters),
    secrets.choice(digits),
    secrets.choice(special)
]

# 4. Fill the remaining length (16 - 3 = 13 characters) from the full pool
password_list += [secrets.choice(all_characters) for _ in range(13)]

# 5. Shuffle the list so the guaranteed characters aren't always at the start
# We use secrets.SystemRandom() to ensure the shuffle is cryptographically secure
secrets.SystemRandom().shuffle(password_list)

# 6. Join into a single string
password = "".join(password_list)

print(password)