map function in python can be used. It takes two arguments. First argument is the function which has to be used for each element of the list. Second argument is the iterable.
a = [1, 2, 3]
map(str, a)
['1', '2', '3']
After converting the list into string you can use simple join function to combine list into a single string
a = map(str, a)
''.join(a)
'123'