Sum in Python is a function built into the Python interpreter. It is used to perform addition and return a value that is stored in a defined variable ready to be manipulated by the program logic.
The sum function begins its operations from the left to right, adding all the iterable pieces until it returns the total. The said items are normal numbers. For instance, to add 4, 6 and 7, the function first stores 4, then increments the value with 6 and finally increments the sum of the first two numbers with 7 to reach the final total. The sum function has a default starting point of 0. This function does not accept a string as the first value.