In python, adding elements in an array can be easily done with the help of extend(),append() and insert() functions.
Consider the following example:
x=arr.array('d', [11.1 , 2.1 ,3.1] )
x.append(10.1)
print(x) #[11.1,2.1,3.1,10.1]
x.extend([8.3,1.3,5.3])
print(x) #[11.1,2.1,3.1,10.1,8.3,1.3,5.3]
x.insert(2,6.2)
print(x) # [11.1,2.1,6.2,3.1,10.1,8.3,1.3,5.3]