import string
import secrets

# Returns a randomly generated sequence of characters of provided length with at least one digit and upper case letter.
# The first character must be a letter. It will also ensure that at least one character in the parameter, symbols, is provided
# Input:
#   length: Int; Length of the random sequence. Default is 8.
#   chars: String; Character set for generating random character. Default is all letters and numbers.
#   symbols: String; Additional characters to add to character set Default is None.
# Output:
#   passwd: String; Contains none if length provided is less than 4. Otherwise contains the random sequence as a string.
def password_generator(length=8, chars=string.ascii_letters + string.digits, symbols=None):
    if length < 4:
        return None

    secrets.SystemRandom()
    if symbols is not None:
        chars = string.ascii_letters + string.digits + symbols
    while True:
        passwd = ''.join(secrets.choice(chars) for i in range(length))
        if symbols:
            if (any(c.islower() for c in passwd)
                    and any(c.isupper() for c in passwd)
                    and any(c.isdigit() for c in passwd)
                    and passwd[0].isalpha()
                    and any((c in symbols) for c in passwd)):
                break
        else:
            if (any(c.islower() for c in passwd)
                    and any(c.isupper() for c in passwd)
                    and any(c.isdigit() for c in passwd)
                    and passwd[0].isalpha()):
                break
    return passwd