How to 'update' or 'overwrite' a python list
You may try this
alist[0] = 2014
but if you are not sure about the position of 123 then you may try like this:
for idx, item in enumerate(alist):
if 123 in item:
alist[idx] = 2014
What about replace the item if you know the position:
aList[0]=2014
Or if you don't know the position loop in the list, find the item and then replace it
aList = [123, 'xyz', 'zara', 'abc']
for i,item in enumerate(aList):
if item==123:
aList[i]=2014
break
print aList