1、指定变量数据类型
在Python中，当将值分配给变量时，将设置数据类型：
示例 | 数据类型 |
x = "Hello World" | str |
x = 20 | int |
x = 20.5 | float |
x = 1j | complex |
x = ["c", "python", "java"] | list |
x = ("c", "python", "java") | tuple |
x = range(6) | range |
x = {"name" : "python", "age" : 20} | dict |
x = {"c", "python", "java"} | set |
x = frozenset({"c", "python", "java"}) | frozenset |
x = True | bool |
x = b"Hello" | bytes |
x = bytearray(5) | bytearray |
x = memoryview(bytes(5)) | memoryview |
2、通过构造函数指定数据类型
如果要指定数据类型，则可以使用以下构造函数：
示例 | 数据类型 |
x = str("Hello World") | str |
x = int(20) | int |
x = float(20.5) | float |
x = complex(1j) | complex |
x = list(("c", "python", "java")) | list |
x = tuple(("c", "python", "java")) | tuple |
x = range(6) | range |
x = dict(name="cjavapy", age=3) | dict |
x = set(("c", "java", "python")) | set |
x = frozenset(("c", "python", "java")) | frozenset |
x = bool(5) | bool |
x = bytes(5) | bytes |
x = bytearray(5) | bytearray |
x = memoryview(bytes(5)) | memoryview |
3、Python常用数据类型示例
shoplist = ['apple', 'mango', 'carrot', 'banana']
print('I have ', len(shoplist), ' items to purchase.')
print('These items are: ', end = '')
for item in shoplist:
print(item, end = ' ')
print('\nI also have to buy rice.')
shoplist.append('rice')
print('My shopping list is now ', shoplist)
print('I will sort my list now')
shoplist.sort()
print('Sorted shopping list is ', shoplist)
print('The first item I will buy is ', shoplist[0])
olditem = shoplist[0]
del shoplist[0]
print('I bought the ', olditem)
print('My shopping list is now ', shoplist)
zoo = ('python', 'elephant', 'penguin')
print('Number of animals in the zoo is ', len(zoo))
new_zoo = 'monkey', 'camel', zoo
print('Number of cages in the new zoo is ', len(new_zoo))
print('All animals in new zoo are ',new_zoo)
print('Animals brought from old zoo are', new_zoo[2])
print('Last animal brought from old zoo is ', new_zoo[2][2])
print('Number of animals in the new zoo is ', len(new_zoo) - 1 + len(new_zoo[2]))
ab = { 'Swaroop' : 'Swaroop@Swaroopch.com',
'Larry' : 'larry@wall.org',
'Matsumoto' : 'matz@ruby-lang.org',
'Spammer' : 'spammer@hotmail.com'
}
print("Swaroop's address is ", ab['Swaroop'])
del ab['Spammer']
print('\nThere are {0} contacts in the address-book\n'.format(len(ab)))
for name, address in ab.items():
print('Contatc {0} at {1}'.format(name, address))
ab['Guido'] = 'guido@python.org'if'Guido'in ab:
print("\nGuido's address is ", ab['Guido'])
name = 'Swaroop'
print('Item 0 is ', shoplist[0])
print('Item 1 is ', shoplist[1])
print('Item 2 is ', shoplist[2])
print('Item 3 is ', shoplist[3])
print('Item -1 is ', shoplist[-1])
print('Item -2 is ', shoplist[-2])
print('Character 0 is ', name[0])
print('Item 1 to 3 is ',shoplist[1:3])
print('Item 2 to end is ',shoplist[2:])
print('Item 1 to -1 is ',shoplist[1:-1])
print('Item start to end is ',shoplist[:])
print('Character 1 to 3 is ', name[1:3])
print('Character 2 to end is ', name[2:])
print('Character 1 to -1 is ', name[1:-1])
print('Character start to end is ', name[:])
bri = set(['brazil', 'russia', 'India', 'China'])
print('India'in bri)
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