加成

a, b = 1, 2

# Using the "+" operator:
a + b                  # = 3

# Using the "in-place" "+=" operator to add and assign:
a += b                 # a = 3 (equivalent to a = a + b)

import operator        # contains 2 argument arithmetic functions for the examples

operator.add(a, b)     # = 5  since a is set to 3 right before this line

# The "+=" operator is equivalent to: 
a = operator.iadd(a, b)    # a = 5 since a is set to 3 right before this line

可能的组合（内置类型）：

• int 和 int（给一个 int）
• int 和 float（给一个 float）
• int 和 complex（给一个 complex）
• float 和 float（给一个 float）
• float 和 complex（给一个 complex）
• complex 和 complex（给一个 complex）

注意：+运算符也用于连接字符串，列表和元组：

"first string " + "second string"    # = 'first string second string'

[1, 2, 3] + [4, 5, 6]                # = [1, 2, 3, 4, 5, 6]