Introducing Python Numbers

下面来通过实例学习一下 Python 内置的 Numbers 类型，及其常用操作符、表达式等。以及随机数的操作。

Operators

$ python
Python 2.7.5 (default, Aug 25 2013, 00:04:04)
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.0.68)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

# 整数
>>> 2
2
>>> -3
-3
>>> int(-12.3)
-12

# 浮点数
>>> 2.0
2.0
>>> float(3)
3.0
>>> float(-3)
-3.0

# 求和
>>> 2 + 3
5

# 差值
>>> 2 - 3
-1

# 相除
>>> 1 / 2
0
>>> 1.0 / 2.0
0.5

# 整除
>>> 10.0 // 2.0
5.0
>>> 10.0 // 5.0
2.0
>>> 10.0 // 15.0
0.0

# 取余
>>> 3 % 2
1
>>> 3 % 5
3
>>> 3.0 % 2.0
1.0

# 乘方
>>> 2 ** 2
4
>>> (-3) ** 2
9

Methods

# 取绝对值
>>> abs(-2)
2

# 取整四舍五入
>>> round(3.23)
3.0
>>> round(3.53)
4.0

# 乘方 x**y
>>> pow(2,2)
4
>>> pow(-3,2)
9

# math 函数
>>> import math

# the largest integer not greater than x
>>> math.floor(1.23)
1.0

#the smallest integer not less than x
>>> math.ceil(1.23)
2.0

# 开方
>>> math.sqrt(4)
2.0

Random Number Functions

>>> import random

# 随机生成六位短信验证码
>>> random.randint(100000, 999999)
195220
>>> random.randint(100000, 999999)
410185


# 随机生成八位小写字母的字符串
>>> import string
>>> ''.join(random.choice(string.ascii_lowercase) for x in range(8))
'danwkfzk'


# 从 list 中随机选择一个数据
>>> user_ids = [100, 200, 300, 400, 500, 600]
>>> user_ids
[100, 200, 300, 400, 500, 600]
>>> random.choice(user_ids)
200
>>> random.choice(user_ids)
100


# 随机选择 3~5 个 list 中的数据
>>> fake_user_ids = []
>>> loop_count = random.randint(3, 5)
>>> loop_count
4
>>> while(loop_count > 0):
...   user_id = random.choice(user_ids)
...   if user_id not in fake_user_ids:
...     print user_id
...     fake_user_ids.append(user_id)
...     loop_count -= 1
...
500
200
600
100
>>> fake_user_ids
[500, 200, 600, 100]


# 根据数据，循环
>>> for i in xrange(3):
...   print i
...
0
1
2

2014-05-15