数据类型

0. 概念

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• 理解：对程序处理的数据，进行的 分类
• 举例

  # 处理的数据是数值类型
  print(1)
  
  # 处理得数据是字符串类型
  print("abc")
  

• Python 是属于 强类型 和 动态类型 的语言

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1. 作用

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• 区分存储空间：不同的数据类型，存储的 空间大小 可能不同

  a = 100
  b = True
  c = 10000000000000000000000000000000
  d = 1.1
  e = ""
  f = []
  g = ()
  h = {}
  i = set([])
  j = complex(1, 2)
  j2 = 1 + 2j
  print(" %s size is %d " % (type(a), sys.getsizeof(a)))
  print(" %s size is %d " % (type(b), sys.getsizeof(b)))
  print(" %s size is %d " % (type(c), sys.getsizeof(c)))
  print(" %s size is %d " % (type(d), sys.getsizeof(d)))
  print(" %s size is %d " % (type(e), sys.getsizeof(e)))
  print(" %s size is %d " % (type(f), sys.getsizeof(f)))
  print(" %s size is %d " % (type(g), sys.getsizeof(g)))
  print(" %s size is %d " % (type(h), sys.getsizeof(h)))
  print(" %s size is %d " % (type(i), sys.getsizeof(i)))
  print(" %s size is %d " % (type(j), sys.getsizeof(j)))
  print(" %s size is %d " % (type(j2), sys.getsizeof(j2)))
  

• 根据不同数据类型的 特性，做不同的 数据处理

  num = 6 + 6
  print(num)
  
  appendStr = "6" + "6"
  print(appendStr)
  

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2. 分类

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• Numbers(数值类型)

  # int
  num = 100
  print(type(num), num)
  
  # Python2.x: 有 long 类型, Python3.x: 无 long 类型
  long_num = 100L
  print type(long_num), long_num
  
  # float
  float_num = 11.11
  print(type(float_num), float_num)
  
  # complex
  complex_num = complex(1, 2)
  print(type(complex_num), complex_num)
  

• Bool(布尔类型)

  is_open = True
  print(type(is_open), is_open)
  

• String(字符串)

  name = "秦子阳"
  print(type(name), name)
  

• List(列表)

  score_list = [100, 99, 88, 66, 59]
  print(type(score_list), score_list)
  

• Tuple(元组)

  name_tuple = ("wxx", "qtt", "xdy", "xfq", "lm", "lb")
  print(type(name_tuple), name_tuple)
  

• Dictory(字典)

  person_dict = {"name": "wxx", "age": 18, "address": "杭州市"}
  print(type(person_dict), person_dict)
  

• Set(集合)

  num_set = {1, 3, 5, 7, 9}
  print(type(num_set), num_set)
  

• NoneType(空类型)

  score_list = [100, 99, 88, 66, 59]
  result = score_list.clear()
  print(type(result), result)
  

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3. 查看

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• 方法：可以使用 type() 查看数据类型

  num = 100
  print(type(num))
  

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4. 转换

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• 强制类型转换：将一个数据 转换 成 指定 的类型，方便处理

  # 格式：类型(需要转换的值)
  numStr = "66"
  a = int(numStr) + 6
  print(a)
  

• 隐式类型转换：较低精度 操作数被 自动转换 成 较高精度 的数据类型

  a = 20
  b = 32.0
  c = a + b
  print(type(c), c)
  

• 转换图
  
  类型转换.png

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