#### 使用表描述式的一些实例
##a1 = []
##for i in range(20) :
##    a1.append(0)
##    
##a2 = [0 for i in range(20)]
##
##a3 = [0]*20

lst1 = [x**2 for x in range(10)]
print("lst1:", lst1)

lst2 = [x for x in range(200) if x%7 == x % 19]
print("lst2:", lst2)

lst3 = [s*2 for s in "abcdefg"]
print("lst3:", lst3)

lst4 = [s+t for s in "abcd" for t in "123"]
print("lst4:", lst4)

lst5 = [s+t for s in "abcd" for t in "123"
        if (ord(s)+ord(t))%2 == 0]
print("lst5:", lst5)

## 如果 is_prime 有定义，则可以写
# [x for x in range(1000) if is_prime(x)]