模块源码：
Source code: Lib/random.py
文档：http://docs.python.org/2/library/random.html
常用方法：
random.random()
Return the next random floating point number in the range [0.0, 1.0).
random.randint(a, b)包括b
Return a random integer N such that a <= N <= b.
random.uniform(a, b)
Return a random floating point number N such that a <= N <= b for a <= b and b <= N <= a for b < a.
The end-point value b may or may not be included in the range depending on floating-point rounding in the equation a + (b-a) *random().
用于生成一个指定范围内的随机符点数，两个参数其中一个是上限，一个是下限。如果a > b，则生成的随机数n: b <= n <= a。如果 a <b， 则 a <= n <= b。
print random.uniform(10, 20)
print random.uniform(20, 10)
#---- 结果（不同机器上的结果不一样）
#18.7356606526
#12.5798298022
random.choice(seq)
Return a random element from the non-empty sequence seq. If seq is empty, raises IndexError.
这个写代码可能会用到。
random.randrange(stop) random.randrange(start, stop[, step])
Return a randomly selected element from range(start, stop, step). This is equivalent to choice(range(start, stop, step)), but doesn’t actually build a range object.
记住常用的就可以了。