Python TypeError: ‘type’ object is not iterable

If you query type(a), you get list. You probably want to do a mapping of the elements to the corresponding types, so use map:

def listType(a):
    new_string = ""
    numSum = 0
    for value in map(type,a):
        if isinstance(value,int) or isinstance(value,float):
            numSum += value
        elif isinstance(value,str):
            new_string += value  

    if new_string and numSum:
        print "String:", new_string
        print "Sum:", numSum
        print "This list is of mixed type"
    elif new_string:
        print "String:", new_string
        print "This list is of string type"
    else:
        print "Sum:", numSum
        print "This list is of integer type"

listType(a)

Furthermore you should not print the result of listType, since it does not return anything, and fix the indentation of the program. I hope it is correct now.