from random import randint

#### 带有默认值的参数

l1 = [i for i in range(1, 10)]
l2 = [i for i in range(10, 20)]

##print("l1 =", l1)
##print("l2 =", l2)
##def accum(lst, init=0):
##    nsum = init
##    for x in lst:
##        nsum += x
##    return nsum
##
##a = accum(l1)
##b = accum(l2, a)
##print(a, b)

##def accum1(lst, init=0, num=-1):
##    nsum = init
##    if num < 0:
##        num = len(lst)
##    for i in range(num):
##        nsum += lst[i]
##    return nsum
##
##a = accum1(l1, 31)
##b = accum1(l1, 10, 6)
##c = accum1(l1, num=6)
##print(a, b, c)

#### 函数形参和调用时实参的一些情况
##def func(a, *b, c=0, d=1):
##    print(a, b, c, d)
##    return 0
##
##func(1, 2, 3, d=10)
##func(1)

##def func(a, b=0, *c, d=11):
##    print(a, b, c, d)
##    return 0
##
##func(1, 2, 3, 4, 5)
##func(1, 2, 3, d=10)
##func(1)

#### 表构造和变动性
##list1 = [0] * 10
##list10 = list1.copy()
##list2 = [[]] * 10
##list20 = list2.copy()
##list3 = [[] for i in range(10)]
##list30 = list3.copy()
##list1[1] = 3
##list2[1].append(1)
##list3[1].append(1)


#### 函数的带默认值的参数，变动对象引起的共享
##def insert(args, start=[]):
##    for x in args:
##        start.append(x)
##    return start
##
##t1 = (1, 2, 3, 4)
##print(t1)
##t2 = [randint(1, 20) for i in range(10)]
##print(t2)
##
##list1 = insert(t1)
##print(list1)
##list2 = insert(t2)
##print(list1)
##print(list2)


### 一个简单生成器
##def nat(limit):
##    for n in range(limit):
##        yield n
##
##for i in nat(10):
##    print(i)


### 在生成器中可以混合使用 yield and return
### 注意: 生成器的返回值对循环的迭代没有影响
##def nat(limit):
##    n = 0
##    while True:
##        n += 1
##        if n > limit:
##            return n
##        yield n
##
##for i in nat(10):
##    print(i)


### 一个生成器：生成参数表中所有正数
##def positive(lst):
##    for x in lst:
##        if (isinstance(x, int) or isinstance(x, float)) and x > 0.0:
##            yield x
##
##ll = [1, "abc", -0.3, -2, 3.12, 0, 2, 1.27, 5]
##for x in positive(ll):
##    print(x)
##print()


##for x in filter(lambda x: (isinstance(x, int) or
##                           isinstance(x, float)) and x > 0.0,
##                ll):
##    print(x)


#### 生成直至 n 的Fibonacci数
##def gen_fib(n):
##    n1 = 0
##    n2 = 1
##    for i in range(n+1):
##        yield n2
##        n1, n2 = n2, n1+n2
##
##for n in gen_fib(10):
##    print(n)


### An infinite generator
##def gen_fibs():
##    n1 = 0
##    n2 = 1
##    while True:
##        yield n2
##        n1, n2 = n2, n1+n2
##
##fib = gen_fibs()
##for i in range(20):
##    print(fib.__next__())


### A generator to yield elements of a list circularly
##def circular(seq):
##    i = 0
##    while True:
##        yield seq[i]
##        i = (i + 1) % len(seq)


##for i in range(0, 150, 13):
##    print(str(i).rjust(3), str(i**2).rjust(5), str(i**3).rjust(7))

#### 格式化实例
##print("abc{0:->10s}123".format("hhhhh"), "\n")
##
##print("price:{price:8.2f},   quantity:{quantity:4d}".format(
##          quantity=23, price=1389.99),
##      "\n")
##
##print("abc{:<<10d}123".format(55555))