python学习笔记1---python的基本数据类型
Number:数字
1)整型与浮点型
整数:int(没有short、int、long之分)
浮点数:float(python里面没有单精度和双精度之分)
>>> print('hello world') hello world >>> 1 1 >>> 133434 133434 >>> type(1) <class 'int'> >>> type(-1) <class 'int'> >>> type(1.1) <class 'float'> >>> type(1.111111111111111111) <class 'float'> >>> type(1+0.1) <class 'float'> >>> type(1+1) <class 'int'> >>> type(1+1.0) <class 'float'> >>> type(1*1) <class 'int'> >>> type(1*1.0) <class 'float'> >>> type(2/2) <class 'float'> >>> type(2//2) <class 'int'> >>> 2/2 1.0 >>> 2//2 1 >>> 1//2 //表示整除 0
2)10、2、8、16进制
>>> 10进制,2进制,8进制,16进制 SyntaxError: invalid character in identifier >>> 0,1,2,3。。。。9,10 SyntaxError: invalid character in identifier >>> 0,1,10 SyntaxError: invalid character in identifier >>> 0,1。。。。7,10 SyntaxError: invalid character in identifier >>> 0,1,2.。。。。。。。9,A,B,C,D,E,F SyntaxError: invalid character in identifier
表示方法:
二进制(0b10)
八进制(0o10)
十六进制(0x10)
>>> 0b10 2 >>> 0b11 3 >>> 0o10 8 >>> 0o11 9 >>> 0x10 16 >>> 0x11 17
进制转换
- 转换为二进制
>>> bin(10) '0b1010' >>> bin(0o7) '0b111' >>> bin(0xE) '0b1110'
- 转换为十进制
>>> int(0b111) 7 >>> int(0o77) 63
- 转换为十六进制
>>> hex(888) '0x378' >>> hex(0o7777) '0xfff'
- 转换为八进制
>>> oct(0b111) '0o7' >>> oct(0x777) '0o3567'
3)bool 布尔类型(数字类型的一种):表示真、假
>>> True True >>> False False >>> true Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> true NameError: name 'true' is not defined >>> false Traceback (most recent call last): File "<pyshell#3>", line 1, in <module> false NameError: name 'false' is not defined >>> type(True) <class 'bool'> >>> type(False) <class 'bool'> >>> int(True) 1 >>> int(False) 0 >>> bool(1) True >>> bool(0) False >>> bool(2) True >>> bool(-1.1) True >>> bool(0b01) True >>> bool(0b0) False >>> bool('abc') True >>> bool('') False >>> bool([1,2,3]) True >>> bool([]) False >>> bool({1,1,1}) True >>> bool({}) False >>> bool(None) False
4)complex 复数
>>> 36j 36j
str 字符串
1)单引号
>>> 'hello world' 'hello world' >>> 'let\'s go' "let's go"
2)双引号
>>> "hello world" 'hello world' >>> 'let's go' SyntaxError: invalid syntax >>> "let's go" "let's go"
3)三引号(多行字符串)
>>> ''' hello world hello world hello world ''' '\nhello world\nhello world\nhello world\n' >>> """ hello world hello world hello world """ '\nhello world\nhello world\nhello world\n' >>> """hello world\nhello world\nhello world""" 'hello world\nhello world\nhello world' >>> print("""hello world\nhello world\nhello world""") hello world hello world hello world >>> print('''hello world\nhello world\nhello world''') hello world hello world hello world >>> print("hello world\nhello world\nhello world") hello world hello world hello world >>> """hello world hello world""" 'hello world\nhello world' >>> 'hello SyntaxError: EOL while scanning string literal >>> 'hello\ world' 'helloworld'
4)转义字符(特殊的字符)
无法“看见”的字符
与语言本身语法有冲突的字符
- n 换行
- ' 单引号
- t 横向制表符
- n 换行
- r 回车
>>> print('hello \n world') hello world >>> print("'hello \n world'") 'hello world' >>> print("'hello \\n world'") 'hello \n world' >>> print('hello \\n world') hello \n world >>> print('c:\northwind\northwest') c: orthwind orthwest >>> print('c:\\northwind\\northwest') c:\northwind\northwest >>> print(r'c:\northwind\northwest') c:\northwind\northwest >>> r'C:\Windows' 'C:\\Windows' >>> R'C:\Windows' 'C:\\Windows' //字符串前加上“r”以后就不是一个普通字符串,而是一个原始字符串 >>> print(r' let 's go') SyntaxError: invalid syntax //这里的单引号不是成对出现,已经不是一个字符串,加上“r”也不会是原始字符串
字符串运算 一
>>> "hello" 'hello' >>> "world" 'world' >>> "hello world" 'hello world' >>> "hello"+"world" 'helloworld' >>> "hello"*3 'hellohellohello' >>> "hello" * "world" Traceback (most recent call last): File "<pyshell#5>", line 1, in <module> "hello" * "world" TypeError: can't multiply sequence by non-int of type 'str' >>> "hello world"[0] 'h' >>> "hello world"[3] 'l' >>> "hello world"[4] 'o' >>> "hello world"[5] ' ' >>> "hello world"[-1] 'd' >>> "hello world"[-3] 'r' //[-n]表示从字符串的末尾往前数n次得到的字符
字符串运算 二
>>> "hello world"[6] 'w' >>> "hello world"[-5] 'w' >>> "hello world"[0:4] 'hell' >>> "hello world"[0:5] 'hello' >>> "hello world"[0:-1] 'hello worl' //这里的-1表示步长 >>> "hello world"[0:-3] 'hello wo'
字符串运算 三
>>> "hello world"[6:10] 'worl' >>> "hello world"[6:11] 'world' >>> "hello world"[6:20] 'world' >>> "hello world"[6:-1] 'worl' >>> "hello world"[6:0] '' >>> "hello world"[6:-0] '' >>> "hello world"[6:] 'world' >>> "hello python java c# javascript php ruby"[6:] 'python java c# javascript php ruby' >>> "hello python java c# javascript php ruby"[:-4] 'hello python java c# javascript php ' >>> "hello python java c# javascript php ruby"[0:-4] 'hello python java c# javascript php ' >>> "hello python java c# javascript php ruby"[-4:] 'ruby'
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