1.例一：
>>> for x in range(1,10):
... L.append(x*x)
>>> L
[1, 4, 9, 16, 25, 36, 49, 64, 81]
但是循环太繁琐，而列表生成式则可以用一行语句代替循环生成上面的list：
>>> [x * x for x in range(1,11)]
[1,4,9,16,25,36,49,64,81,100]
>>> [x * x for x in range(1,11) if x%2==0]
[4,16,36,64,100]
>>> [m+n for m in 'abc' for n in 'xyz']
['ax', 'ay', 'az', 'bx', 'by', 'bz', 'cx', 'cy', 'cz']
>>> d = { 'x':'a','y':'b','z':'c'}
>>> for k,v in d.items():
... print(k, '=', v)
x = a
y = b
z = c
