CSV write

@app.route('/retrieve', methods= ['GET'])

def retriever(): 
    # can be made even more condensed (sure of it)
    a= []
    b=[]
    run=[]
    tim=[]
    a2= []
    b2=[]
    run2=[]
    tim2=[]
    a3= []
    b3=[]
    run3=[]
    tim3=[]
    #appending to arrays
    for i in xrange(1,4): 
        for post in posts.find({"run":i}, {"_id":0}): 
            if i== 1: 
                a.append(post["O1"])
                b.append(post["O2"])
                tim.append(post["date"])
                run.append(post["run"])

            if i==2:                 
                a2.append(post["O1"])
                b2.append(post["O2"])
                tim2.append(post["date"])
                run2.append(post["run"])

            if i==3: 
                a3.append(post["O1"])
                b3.append(post["O2"])
                tim3.append(post["date"])
                run3.append(post["run"])

    # # saving as csv.. 
    # #how to make this more smart
    for r in xrange(1,4):
        filename= "dat"+str(r)+ "O1.csv"
        filename2= "dat"+str(r)+ "O2.csv"
        with open(filename,'wb') as f: 
            writer= csv.writer(f)
            if r==1: 
                rows= zip(tim, a)
            if r==2: 
                rows= zip(tim2, a2)
            if r==3: 
                rows= zip(tim3, a3)


            for row in rows: 
                writer.writerow(row)

        with open(filename2,'wb') as f2: 
            writer= csv.writer(f2)
            if r==1: 
                rows= zip(tim, b)
            if r==2: 
                rows= zip(tim2, b2)
            if r==3: 
                rows= zip(tim3, b3)


            for row in rows: 
                writer.writerow(row)