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
python生成1到100之间随机数>>> 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]
>>>

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