Binary to decimal in python

Question

binaryToDecimal = lambda binary: sum([[int(2**index) for index in range(len(binary))][-index-1] for index, char in enumerate(binary) if int(char)])

I wrote a simple function that converts binary strings into decimal integers. How can this be improved/simplified?

I know about the int function, I wanted to implement the conversion myself.

• Jean-François Fabre: what about using python: binaryToDecimal = lambda x: str(int(x,2))
• Hum4n01d: I'm aware that you can do that :) I just wanted to implement it myself
• IEatBagels: Well, readability could be improved a lot by not using too much list comprehensions together :)
• Hum4n01d: Definitely, I did that on purpose though to make it as compact as possible
• Daniel: I added reinventing-the-wheel, because that's what you're doing here: inventing this even though a standard implementation exists. In the future, you may want to add this tag yourself, to signify to other users that you're knowingly not using the standard implementation.

Answer 1

Of course, the most efficient solution would be to let python parse the binary string as integer ;)

binaryToDecimal = lambda x: int(x,2)

But you already know that, so what about simplifying your code like this:

binaryToDecimal = lambda binary: sum(1<<(len(binary)-index-1) for index, char in enumerate(binary) if char=='1')

• removing the creation of the inner list comprehension just to pick one value
• not using power but bitshift (integer computation, faster, more accurate)
• don't create a list to pass to sum, pass a generator comprehension (it's faster, saves memory)
• in your condition, don't convert your number to integer, just test against the char value (it's faster)

Keep in mind that your parsing has no error checking!

• Hum4n01d: Funny enough, I tested the character at first but moved to int to save characters (I was challenging myself to use the least characters)
• Jean-François Fabre: yes, it's good for code golfing, but not really for performance :)