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基本运算符
该部分讲解了如何在 Python 中使用基本运算符。
算术运算符
与其他编程语言一样，加、减、乘、除运算符可以用于数字操作。
number = 1 + 2 * 3 / 4.0
print(number)
试着预测答案会是多少。Python 是否遵循运算优先级？
另一个可用的运算符是取模（%）运算符，它返回除法的整数余数。 被除数 % 除数 = 余数。
remainder = 11 % 3
print(remainder)
使用两个乘号表示幂运算关系。
squared = 7 ** 2
cubed = 2 ** 3
print(squared)
print(cubed)
使用字符串运算符
Python 支持使用加号运算符连接字符串：
helloworld = "hello" + " " + "world"
print(helloworld)
Python 也支持通过乘法运算符重复字符串形成新的字符串：
lotsofhellos = "hello" * 10
print(lotsofhellos)
使用列表运算符
可以通过加法运算符连接列表：
even_numbers = [2,4,6,8]
odd_numbers = [1,3,5,7]
all_numbers = odd_numbers + even_numbers
print(all_numbers)
就像字符串一样，Python 支持使用乘法运算符形成有重复序列的新列表：
print([1,2,3] * 3)
Exercise
该练习的目标是创建两个列表，分别命名为 x_list 和 y_list，其中包含 10 个变量 x 和 y 的实例。还需要创建一个名为 big_list 的列表，通过连接你创建的两个列表，使其包含 10 次变量 x 和 y。
x = object()
y = object()
# TODO: change this code
x_list = [x]
y_list = [y]
big_list = []
print("x_list contains %d objects" % len(x_list))
print("y_list contains %d objects" % len(y_list))
print("big_list contains %d objects" % len(big_list))
# testing code
if x_list.count(x) == 10 and y_list.count(y) == 10:
print("Almost there...")
if big_list.count(x) == 10 and big_list.count(y) == 10:
print("Great!")
x = object()
y = object()
# TODO: change this code
x_list = [x] * 10
y_list = [y] * 10
big_list = x_list + y_list
print("x_list contains %d objects" % len(x_list))
print("y_list contains %d objects" % len(y_list))
print("big_list contains %d objects" % len(big_list))
# testing code
if x_list.count(x) == 10 and y_list.count(y) == 10:
print("Almost there...")
if big_list.count(x) == 10 and big_list.count(y) == 10:
print("Great!")
Ex().check_object('x_list').has_equal_value(expr_code = 'len(x_list)')
Ex().check_object('y_list').has_equal_value(expr_code = 'len(y_list)')
Ex().check_object('big_list').has_equal_value(expr_code = 'len(big_list)')
success_msg('Good work!')
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