Python sum() Function

Python sum() function is used to get the sum of numbers of an iterable.

Python sum() function syntax is:

sum(iterable[, start])

start is an optional number with default value of 0. If start is provided, then the sum of start and all the numbers in the iterable is returned.

Python sum() List of Numbers

s = sum([1, 2, 3])
print(s)

s = sum([1, 2, 3], 10)
print(s)

Output:

6
16

Note that sum() method doesn’t take keyword arguments, so if we write sum([1, 2, 3], start=10) then it will throw exception as TypeError: sum() takes no keyword arguments.

Python Sum of a Sequence of Integers

Since sum accepts iterable as argument, we can pass tuple, bytes of numbers too.

s = sum(bytes([1, 2]))
print(s)

s = sum(bytearray([1, 2]), 10)
print(s)

# sum of integers in different formats, tuple of numbers
s = sum((1, 0b11, 0o17, 0xFF))
print(s)

s = sum((1, 0b11, 0o17, 0xFF), 0xF)
print(s)

Output:

3
13
274
289

Python Sum of Floats

s = sum([1.5, 2.5, 3])
print(s)

Output: 7.0 If you want to add floating point values with extended precision, you can use math.fsum() function.

Python Sum of Complex Numbers

sum() function works with complex numbers too.

s = sum([1 + 2j, 3 + 4j])
print(s)

s = sum([1 + 2j, 3 + 4j], 2 + 2j)
print(s)

s = sum([1 + 2j, 2, 1.5 - 2j])
print(s)

Output:

(4+6j)
(6+8j)
(4.5+0j)