How to add list together
<p>I'm trying to figure out a question and I'm getting confused. Basically I have a list and it's supposed to represent a bank statement. I'm trying to add the list together so the negative numbers, which is supposed to represent withdrawl, is added together and the positive numbers are added together to represent the deposits. So far I got </p>

<pre><code>def statement(l):
    deposit = 0
    withdrawl = 0
    for a in l:
        a = sum(l)
    for b in l:
        if b == -b:
            b = sum(b)        
    return [a,-b]
</code></pre>

<p>but when I do <code>statement([30.95,-15.67,45.56,-55.00,43.78])</code> 
it returns <code>[49.620000000000005, -43.78]</code>
when it is supposed to return <code>[120.29,-70.67]</code> can someone help?</p>

<p>Thanks!</p>
