python,random随机数的获取

　　随机数生成

　　首先我们需要在程序中引入random》》》import random as r

　　r.random()用于生成一个随机的浮点数，

>>> print(r.random())

0.23928059596578843
>>> 

　　r.uniform(10,20)，生成一个随机的浮点数，如果a>b 则a为上限，b为下限。如果a<b，则b为上限

>>> print(r.uniform(10,20))

15.995495884011348
>>> print(r.uniform(20,10))

13.179092381602349
>>> 
#如果没有给定a,b那么会报错

>>> print(r.uniform())

Traceback (most recent call last):
File "<pyshell#5>", line 1, in <module>
print(r.uniform())
TypeError: uniform() missing 2 required positional arguments: 'a' and 'b'
>>> print(r.randint())

　　r.randint(a,b),生成一个随机的整数，a 是下限，b是上限。下限必须小于上限

>>> print(r.randint())

Traceback (most recent call last):
  File "<pyshell#6>", line 1, in <module>
    print(r.randint())
TypeError: randint() missing 2 required positional arguments: 'a' and 'b'
>>> print(r.randint(1,10))

1

　>>> print(r.randint(10,1))
　　Traceback (most recent call last):
　　File "<pyshell#8>", line 1, in <module>
　　print(r.randint(10,1))
　　File "D:\python\lib\random.py", line 222, in randint
　　return self.randrange(a, b+1)
　　File "D:\python\lib\random.py", line 200, in randrange
　　raise ValueError("empty range for randrange() (%d,%d, %d)" % (istart, istop, width))
　　ValueError: empty range for randrange() (10,2, -8)
　>>>

　　r.randrange(a,b,1or2)，随机取出指定范围内的奇偶数，1奇数 2偶数

>>> r.randrange(0,10,2)

6
>>> r.randrange(0,10,1)

1
>>> r.randrange(0,10,1)

7
>>> 

　　r.choice('qwertuiopolkjhgffdsa')所及取出某一个字符

>>> print(r.choice('qwertyuiop[]lkjhgfdsazxcvbnm'))

k
>>> print(r.choice('qwertyuiop[]lkjhgfdsazxcvbnm'))

n
>>> print(r.choice('qwertyuiop[]lkjhgfdsazxcvbnm'))

t
>>> 

　　r.sample(str,num)，会随机输出num个字符，且num一定小于等于len(str)

# 小于字符长度时
>>> r.sample('qweasd',2)

['d', 'q']
# 大于字符长度时
>>> r.sample('qweasd',8)

Traceback (most recent call last):
  File "<pyshell#25>", line 1, in <module>
    r.sample('qweasd',8)
  File "D:\python\lib\random.py", line 319, in sample
    raise ValueError("Sample larger than population or is negative")
ValueError: Sample larger than population or is negative
# 等于字符长度时
>>> r.sample('qweasd',6)

['s', 'd', 'a', 'e', 'w', 'q']
>>> 

　　洗牌，也就是随机排序

>>> items = [1,2,3,4,5,6]

>>> r.shuffle(items)

>>> items

[3, 6, 1, 5, 2, 4]
>>>