一、常用数据类型

整数类型：

a = 11
b = 99
c = 0b110
d = 0xff

浮点类型：

a = 0.01
b = 0.1234
pi = 3.1415926

字符串：

a = "hello world"
a = 'let\'s go'
a = "let's go"

• 单引号字符串与双引号字符串的区别
  '"hello world!" she said'
"\"hello world!\" she said"
  效果 figure1.jpg

' 与"单独出现在字符串时，没有区别
若组合出现在字符串时，需要向上述代码一样进行转换。

• 字符串拼接
  "let's say" '"hello world!"'
'hello '+'world!'

a = 'hello '
b = 'world!'
print(a+b)

• 长字符串
  如果要打印一个非常长的字符串，

print('''This is a very long string. It continues here. And it's not
 over yet. "Hello, world!" Still here.''')

print("""This is a very long string. It continues here. And it's not
 over yet. "Hello, world!"
Still here.""")

效果： figure2.jpg

单独 \ 的用法

print("Hello, \
world!")
print(1+2\
     +3+4\
      +6)
print\
('hello, world')

效果： figure3.jpg

• 原始字符串
  原始字符串即遇到转意符后不发生改变。如

print('hello \n world')
print(r'hello \n world')

效果 figure4.jpg

布尔值：

a = True
b = False

空值：

None

二、常见数据类型

序列：

a = ["张三","李四","王五","赵六","阿帕奇"]

edward = ['Edward Gumby', 42]
john = ['John Smith', 50]
database1 = [edward, john]
database2 = [['Edward Gumby', 42], ['John Smith', 50]]

通用操作-索引

greeting = 'Hello'
greeting[0]
输出:'H'
greeting = 'Hello'
greeting[-1]
输出:'o'
names = ["张三","李四","王五","赵六","阿帕奇"]
print(names[1])
输出：李四
print(names[-2])
输出：赵六

切片

months =['January','February','March','April','May','June','July',\
'August','September','October','November','December']
print(months[2:6])
tag = '<a href="http://www.python.org">Python web site</a>' 
print(tag[9:30])

输出：

['March', 'April', 'May', 'June']
'http://www.python.org'

执行切片操作时，你显式或隐式地指定起点和终点，但通常省略另一个参数，即步长。在普通切片中，步长为1。这意味着从一个元素移到下一个元素。当然，步长不能为0，否则无法向前移动，但可以为负数，即从右向左提取元素。

numbers = [1,2,3,4,5,6,8,9,10]
numbers[0:10:2]

输出

[1, 3, 5, 8, 10]

序列相加

print([1, 2, 3] + [4, 5, 6])
print('Hello,' + 'world!')

输出

[1, 2, 3, 4, 5, 6]
Hello world!

序列乘法

'python' * 5

输出

'pythonpythonpythonpythonpython'

[42] * 10

输出:

[42, 42, 42, 42, 42, 42, 42, 42, 42, 42]

序列成员资格

>>> permissions = 'rw' 12
>>> 'w' in permissions
True
>>> 'x' in permissions
False

>>> database = [['albert', '1234'], ['dilbert', '4242'], \
>>> ['smith', '7524'], ['jones', '9843']]
>>> username = 'smith'
>>> code = '7524'
>>> [username,code] in database
True

长度、最小值和最大值

>>> numbers = [100, 34, 678]
>>> len(numbers) 
3
>>> max(numbers)
678
>>> min(numbers)
34
>>> max(2, 3)
3
>>> min(9, 3, 2, 5) 
2