python实现加减乘除计算：

# coding = utf-8

def add(num1, num2):
    return num1 + num2


def minus(num1, num2):
    return num1 - num2


def multiply(num1, num2):
    return num1 * num2


def divide(num1, num2):
    if num2 == 0:
        print('除数不能为0')
    else:
        return num1 / num2


print('选择运算：')
print('1 是 +')
print('2 是 -')
print('3 是 *')
print('4 是 /')
operator = input('输入您的选择(1/2/3/4)：')
num1 = int(input('输入第一个数：'))
num2 = int(input('输入第二个数：'))
if operator == '1':
    print('{} + {} = {}'.format(num1, num2, add(num1, num2)))
elif operator == '2':
    print('{} - {} = {}'.format(num1, num2, minus(num1, num2)))
elif operator == '3':
    print('{} * {} = {}'.format(num1, num2, multiply(num1, num2)))
elif operator == '4':
    print('{} / {} = {}'.format(num1, num2, divide(num1, num2)))
else:
    print('这不是一个合法的运算符')

运行结果：