python学习笔记1---python的基本数据类型

摘要：数字整型与浮点型整数没有之分浮点数里面没有单精度和双精度之分表示整除进制进制，进制，进制，进制，，，。。。。

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)

>>> type(-1)

>>> type(1.1)

>>> type(1.111111111111111111)

>>> type(1+0.1)

>>> type(1+1)

>>> type(1+1.0)

>>> type(1*1)

>>> type(1*1.0)

>>> type(2/2)

>>> type(2//2)

>>> 2/2
1.0
>>> 2//2
1
>>> 1//2  //表示整除
0

>>> 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"

>>> True
True
>>> False
False
>>> true
Traceback (most recent call last):
  File "", line 1, in 
    true
NameError: name "true" is not defined
>>> false
Traceback (most recent call last):
  File "", line 1, in 
    false
NameError: name "false" is not defined
>>> type(True)

>>> type(False)

>>> 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

>>> 36j
36j

>>> "hello world"
"hello world"
>>> "let"s go"
"let"s go"

>>> "hello world"
"hello world"
>>> "let"s go"
SyntaxError: invalid syntax
>>> "let"s go"
"let"s go"

>>> """
hello world
hello world
hello world
"""
"
hello world
hello world
hello world
"
>>> """
hello world
hello world
hello world
"""
"
hello world
hello world
hello world
"
>>> """hello world
hello world
hello world"""
"hello world
hello world
hello world"
>>> print("""hello world
hello world
hello world""")
hello world
hello world
hello world
>>> print("""hello world
hello world
hello world""")
hello world
hello world
hello world
>>> print("hello world
hello world
hello world")
hello world
hello world
hello world
>>> """hello world
hello world"""
"hello world
hello world"
>>> "hello
SyntaxError: EOL while scanning string literal
>>> "hello
world"
"helloworld"

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 
 world")
hello 
 world
>>> print(""hello 
 world"")
"hello 
 world"
>>> print(""hello 
 world"")
"hello 
 world"
>>> print("hello 
 world")
hello 
 world
>>> print("c:
orthwind
orthwest")
c:
orthwind
orthwest
>>> print("c:
orthwind
orthwest")
c:
orthwind
orthwest
>>> print(r"c:
orthwind
orthwest")
c:
orthwind
orthwest
>>> 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

>>> "hello"
"hello"
>>> "world"
"world"
>>> "hello world"
"hello world"
>>> "hello"+"world"
"helloworld"
>>> "hello"*3
"hellohellohello"
>>> "hello" * "world"
Traceback (most recent call last):
  File "", line 1, in 
    "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

>>> "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"

>>> "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"