Normal Equivalence

• Javascript parseInt(x, 2)
• Python int(x, 2)

Using Same Method as Posted Code

from functools import reduce
import math

def bin2dec(s):
    return reduce(lambda x, y_i: x + int(math.pow(2, y_i[0])) if y_i[1] == '1' else x, 
                  enumerate(reversed(s)), 
                  0)

Test

print(bin2dec('110'))  # outut: 6

Explanation

• reversed(s) to replace Javascript num.split('').reverse()
• Python's reduce function from functools has signature reduce(function, iterable[, initializer])
  • Use Python lambda function in place of Javascript's function(x, y, i){... (1st argument)
  • Javascript reduce provide current value and current index y, i
  • Python only provides current value, so we use enumerate(..) on values array to convert to current index, current value pairs (2nd argument)
  • y_i are value tuples, with y_i[0] = index and y_i[1] the value
  • use 0 as initializer (last argument in reduce)
• int to convert the value of math.pow from float to integer
• Python if else expression in place of Javascript's ? ternary operator

Simpler Python Code than Using Reduce

def bin2dec(s):
    return sum((0, 2**i)[y == '1'] for i, y in enumerate(s[::-1]))

You can just use the built-in int function:

int("010010", 2)

>>> 18

That said I found a pretty interesting alternative approach using js2py. You can feed it the whole js function as a string, allowing you to effectively use js inside python:

import js2py

bin2dec = js2py.eval_js("""
function bin2dec(num){
    return num.split('').reverse().reduce(function(x, y, i){
        return (y === '1') ? x + Math.pow(2, i) : x;
    }, 0);
}
""")

bin2dec("010010")

>>> 18

Install with pip install js2py

You made a lot of mistakes with your attempt, the map function returns an iterator, not a list. Generally, just avoid map and filter and just use a list comprehension instead.

You also raised 2 to the power of the value (1 or 0) when it should have been the index.

Here's a working version of your example:

def bin2dec(num):
    listNum = [int(n) for n in num]
    total = 0
    listNum.reverse()
    for i, n in enumerate(listNum):
        if n == 1:
            total += 2 ** i
    return total