数据的迭代(1.1)

列表

1. filter + lambda函数

   >>> import random
   >>> l1 = [random.randint(-10, 10) for i in range(10)]
   >>> print(l1)
   [3, 8, -5, 4, -4, -5, -7, -8, -6, -7]
   >>> print(list(filter(lambda x: x>0, l1)))
   [3, 8, 4]

2. 迭代器

  >>> print([x for x in l1 if x>0])
  [3, 8, 4]

集合

1. 迭代器

   >>> s1 = set(random.randint(-10, 10) for i in range(10))
   >>> print(s1)
   {-10, -5, -1, 0, 3, 8, 9}
   >>> print({x for x in s1 if x >0})
   {8, 9, 3}
   

字典

• 产生随机字典

  	# 产生随机字典
  	letters = 'abcdefghijklmnopqrstuvwxyz'
  	l2 = []
  	l1 = [0 for i in range(len(letters))]
  	d1 = {}
  	for got_num in range(len(letters)):
  	    temp_int = random.randint(got_num+1, len(letters)) - got_num # 表示第temp_int个0，从1开始
  	    current_num,i  = 0, -1
  	    while current_num < temp_int:
  	        i += 1
  	        current_num += 1 if l1[i] == 0 else 0
  	    # i 就是我们要找的位置
  	    l2.append(i)
  	    l1[i] = 1
  	
  	d1 = {letters[x]: random.randint(-10, 10) for x in l2}
  	# 打印一下
  	print(d1)
  

• d1的迭代

  >>> d2 = {k:v for k,v in d1.items() if v>0}
  >>> print(d2)
  	{'a': 9,
  	 'b': 3,
  	 'c': 5,
  	 'd': 10,
  	 'f': 3,
  	 'i': 8,
  	 'j': 2,
  	 'n': 5,
  	 'v': 1,
  	 'w': 10,
  	 'x': 3}