Python数字和字符串学习笔记（上）

1.正负数
  2.十六进制(表示方式为0x或者0X开头。例如：0xff)
  3.八进制(表示方式为0o或者0O开头。例如：0o632457)
  4.二进制 (表示方式为0b或者0B开头。例如：0b101100)

>>> s=10
>>> bin(s)
'0b1010'
>>> oct(s)
'0o12'
>>> hex(s)
'0xa'

>>> int('0b10010',2)
18
>>> int('0o52415',8)
21773
>>> int('0x134ab',16)
79019
>>> int('s',32)
28
>>> int('yz',36)
1259

>>> hex(0b1001)
'0x9'
>>> hex(0o1234)
'0x29c'
>>> oct(0b101)
'0o5'
>>> oct(0xff)
'0o377'
>>> bin(0xff)
'0b11111111'
>>> bin(0o7777)
'0b111111111111'

>>> a=12
>>> f=~a
>>> f
-13
>>> bin(f)
'-0b1101'
>>> bin(a)
'0b1100'
>>> bin(a<<1)
'0b11000'
>>> bin(a>>1)
'0b110'
>>> list=[1,2,3,4,5]
>>> a=3
>>> print (a in list)
True
>>> print (a not in list)
False
>>> a=['1,2,3,4,5']
>>> b=a
>>> print (b is a )
True
>>> print (b is not a )
False
>>> b=a[:]>>> print (b is a)  #这是因为字符串是不可变的
False
>>> print (id(a))
42473480
>>> print (id(b))
42485000

>>> pow(2,3)
8

>>> import math
>>> math.sqrt(4)
2.0

>>>max(2,3,4,5,1,9,6)
9

>>> min(2,3,4,5,1,9,6)
1

>>> abs(-1)
1
>>> math.fabs(-1)
1.0

>>> round(3.5)
4
>>> round(2.5)
2
>>> round(2.54)
3
>>> round(2.45)
2

>>> math.ceil(1.7)
2
>>> math.ceil(1.3)
2

>>> math.floor(1.7)
1
>>> math.floor(1.3)
1

>>> cmp(1,2)
-1
>>> cmp(1,1)
0
>>> cmp(2,1)
1

>>> import random
>>> random.random()
0.18001643527271916

>>> random.choice([1,2,3,4,5])
2
>>> random.choice([1,2,3,4,5])
3
>>> random.sample([1,2,3,4,5,6,7,8,9],2)
[3, 7]
>>> random.sample([1,2,3,4,5,6,7,8,9],3)
[4, 9, 3]

>>> a=[1,2,3,4,5,8]
>>> random.shuffle(a)
>>> a
[1, 8, 2, 3, 4, 5]

>>> random.getrandbits(6)
55
>>> random.getrandbits(6)
48
>>> random.getrandbits(7)
104

>>> math.modf(1.4)
(0.3999999999999999, 1.0)
>>> math.modf(1.5)
(0.5, 1.0)
>>> math.modf(2.8)
(0.7999999999999998, 2.0)
>>> math.modf(3.1)
(0.10000000000000009, 3.0)

>>> math.log(4,2)
2.0
>>> math.log2(4)
2.0
>>> math.log10(100)
2.0
>>> math.log(100,10)
2.0

>>> s=format(2.345,'0.2f')
>>> s
>>> type (s)
<class 'str'>
>>> round(2.5)
2
>>> format(2.5,'0.0f')
'2'

>>> a=4.2
>>> b=2.1
>>> a+b
6.300000000000001
>>> from decimal import Decimal
>>> a=Decimal('2.1')
>>> b=Decimal('4.2')
>>> a+b
Decimal('6.3')

>>> a=20
>>> bin(a)
'0b10100'
>>> oct(a)
'0o24'
>>> hex(a)
'0x14'
>>> format(a,'b')
'10100'
>>> format(a,'o')
'24'
>>> format(a,'x')
'14'

>>> 'abc'+'def'
'abcdef'
>>> 'hello' *5
'hellohellohellohellohello'
>>> print ('-'*50)
--------------------------------------------------
>>> "aa""bb"
'aabb'
>>> 'ab''cd'
'abcd'

a="text"
>>> for c in a:
...     print (c,end='')
...
text
>>> for c in a:
...     print (c,end='-')
...
t-e-x-t-
>>> 'x' in a 
True
>>> text='this_is_str'
>>> text[0:4]
'this'
>>> text[5:7]
'is'
>>> text[:4]
'this'
>>> text[-3:]
'str'
>>> text[-12:-7]
'this'
>>> text[::2]
'ti_ssr'
>>> text[8:1:-2]
'ss_i'

>>> ord('d')
100
>>> chr(99)
'c'
>>> ord('王')
29579
>>> chr(29579)
'王'

>>> Text=""   #初始化Text
>>> text="aSdFgHjK"  
>>> for i in text:
...     i_code=ord(i)
...     if 97<=i_code and i_code<=122:
...             Text+=chr(i_code-32)
...     else:
...             Text+=i
...
>>> Text'ASDFGHJK'
>>> for x in text:
...     x_code=ord(x)
...     if 65<=x_code and x_code<=90:
...             Text+=chr(x_code+32)
...     else:
...             Text+=x
...
>>> Text
'ASDFGHJKasdfghjk'

>>> str='asdFGHzxcVBN'
>>> str.replace('asd','ASD')
'ASDFGHzxcVBN'