binary - decimal(general)

# Input
bin = int(input("Type a binary number"))
# Process
str_bin = str(bin)
power = 0
lengh = len(str_bin)
total = 0
while lengh  > 0:
    unit = str_bin[lengh-1: lengh]
    int_unit = int(unit)
    total += int_unit * 2 ** power
    power += 1
    lengh -= 1
print("The decimal value for this binary number is", total)