[Python基础]003.语法(2)

语法(2)

运算符
代码规范
流程控制
- pass
- if
- while
- for
- break
- continue

运算符

数学运算

+ ：加
- ：减
* ：乘
/ ：除
% ：取模
** ：幂
// ：取整除

代码

i = 3

j = 2

k = i + j       #

k = i - j       #

k = i * j       #

k = i / j       #

k = i % j       #

k = i ** j      #

k = i // j      #

比较运算

== 或者 is ：等于
!= 或者 is not 或者 <>：不等于
> ：大于
< ：小于
>= ：大等于
<= ：小等于

代码

i = 3

j = 2

i is j          # False

i == j          # False

i is not j      # True

i != j          # True

i <> j          # True

i > j           # True

i < j           # False

i >= j          # True

i <= j          # False

逻辑运算

and ：与运算
or ：或运算
not ：非运算

代码

i = True

j = False

i and j         # False

i or j          # True

not i           # False

not (i and j)   # True

位运算

& ：与
| ：或
^ ：异或
~ ：反
<< ：左移
>> ：右移

代码

i = 10

j = 20

i & j           #

i | j           #

i ^ j           #

~i              # -11

i << 2          #

i >> 2          #

赋值运算

= ：直接赋值 a = b
+= ： a += b 等效于 a = a + b
-= ： a -= b 等效于 a = a - b
*= ： a *= b 等效于 a = a * b
/= ： a /= b 等效于 a = a / b
%= ： a %= b 等效于 a = a % b
**= ： a **= b 等效于 a = a ** b
//= ： a //= b 等效于 a = a // b

代码

i = 10

i += 10         #

# 其他运算符同上

其他运算

in ：判断是否在序列里

代码

i = 10

l = [1, 2, 4, 8, 10]

a = i in l              # True

代码规范

代码缩进

Python不使用其他语言的 大括号{ } 或 end 等来区分代码块，而使用缩进。
缩进的数量为 4 ，所有代码块都必须严格执行，否则执行时会出错。

i = 10

j = 20

if i == 10:

    print 'i == 10'         # 缩进4格

    if j == 10:

        print 'j == 10'     # 再缩进4格

多行

当语句太长时，Python使用 斜杠\ 来分割。

注释

单行注释
Python中单行注释以 # 开始。

  do_something        # 注释 可在行末尾

块注释 Python中的块注释用 三引号''' 包围。

  '''

  块注释

  可包含多行

  '''

  def fun():

      pass

流程控制

pass

空语句 pass ，保证程序完整

# do_somegthing...

pass

if

条件语句

if 条件: ， else:

  sd_members = ['AC', 'Horse', 'Monut']

  if 'AC' in sd_members:

      print 'AC'

  else:

      pass

if 条件: ， elif 条件: ， else:

  sd_members = ['AC', 'Horse', 'Monut']

  if 'AC' in sd_members:

      print 0

  elif 'Horse' in sd_members:

      print 1

  else:

      print 2

while

循环语句 while 条件:

i = 0

while i == 10:

    print i

    i = i + 1

输出为 0 1 2 3 4 5 6 7 8 9 10

for

循环语句 for .. in ..:

for i in range(10):

    print i

range(x)生成一个 0 ~ 9 的数组
输出为 0 1 2 3 4 5 6 7 8 9

break

控制语句 终止循环

for i in range(10):

    print i

    if i == 5:

        break

当 i 等于 5 时，终止循环。
输出为 0 1 2 3 4 5

continue

控制语句 跳出该次循环，执行下一次

for i in range(10):

    if i == 5:

        continue

    print i

当 i 等于 5 时，跳出循环。输出为 0 1 2 3 4 6 7 8 9

本站文章为宝宝巴士 SD.Team原创，转载务必在明显处注明：（作者官方网站：宝宝巴士)
转载自【宝宝巴士SuperDo团队】 原文链接: http://www.cnblogs.com/superdo/p/4495553.html

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