哪位能把下面这段javascript 转成Python

function B(a){var b="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";var c,d,e,f,g,h,i,j,k=0,l=0,m="",n=[];if(!a){return a}a+="";do{f=b.indexOf(a.charAt(k++));g=b.indexOf(a.charAt(k++));h=b.indexOf(a.charAt(k++));i=b.indexOf(a.charAt(k++));j=f<<18|g<<12|h<<6|i;c=j>>16&255;d=j>>8&255;e=j&255;if(h==64){n[l++]=String.fromCharCode(c)}else if(i==64){n[l++]=String.fromCharCode(c,d)}else{n[l++]=String.fromCharCode(c,d,e)}}while(k<a.length);m=n.join("");return m}

应该是这样的：
def B(a):
    b="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    k=0
    m=""
    n=[];
    if not a:
        return a
    a+=""

    while True:
        f=b.find(a[k])
        k += 1
        g=b.find(a[k])
        k += 1
        h=b.find(a[k])
        k += 1
        i=b.find(a[k])
        k += 1
        j=f<<18|g<<12|h<<6|i
        c=j>>16&255;
        d=j>>8&255;
        e=j&255;
        if h==64:
            n.append(chr(c))
        elif i==64:
            n.append(chr(c)+chr(d))
        else:
            n.append(chr(c)+chr(d)+chr(e))
        if k>=len(a):
            break

    m = "".join(n)

    return m


print B('ABCDEFGH')