python学习之杂记
2017-10-14 00:18
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以下参考官方文档
0关于计算
>>> tax = 12.5 / 100 >>> price = 100.50 >>> price * tax 12.5625 #交互式模式下,变量临时值赋给"_",so,可以利用"_"连续计算 >>> price + _ 113.0625 >>> round(_, 2) 113.06
1字符串连接
>>> 'Py' 'thon' #与'Py'+'thon'等效 'Python'
2关于字符串
>>> word = 'Python' #>>> word[0] = 'J' # ... #TypeError: 'str' object does not support item assignment >>> 'J' + word[1:] #新建一个字符串 'Jython' #>>> word[2:] = 'py' # ... #TypeError: 'str' object does not support item assignment >>> word[:2] + 'py' #新建一个字符串 'Pypy'
3 other
>>> x = set ('spam') >>> y = {'h','a','m'} >>> x,y ({'s', 'm', 'a', 'p'}, {'h', 'm', 'a'}) >>> x & y {'m', 'a'} >>> x | y {'s', 'm', 'p', 'h', 'a'} >>> x - y {'s', 'p'} >>> {n**2 for n in [1,2,3,4]} {16, 1, 4, 9} >>> list(set([1,2,1,3,1,2,4,1])) [1, 2, 3, 4] >>> set('spam')-set('ham') {'s', 'p'} >>> set('spam')==set('maps') True >>> 'p' in set ('spam'),'p' in 'spam','ham' in ['eggs','spam','ham'] (True, True, True)
4 math
>>> import math >>> math.floor(2.5) 2 >>> math.floor(-2.5) -3 >>> math.trunc(2.5) 2 >>> math.trunc(-2.5) #这里有区别 -2 >>> 1j*1j (-1+0j) >>> 2+1j*3 (2+3j) >>> (2+3j)*3 (6+9j) >>> math.pi,math.e (3.141592653589793, 2.718281828459045) >>> math.sqrt(144),math.sqrt(2) (12.0, 1.4142135623730951) >>> min(1,2,3,4,5,-1,-2,-5),max(1,2,3,4,5,-1,-2,-5) (-5, 5) >>> sum((1,2,3,4,5)) 15
5 Hex Octal Binary
>>> 0o1,0o10,0o377 (1, 8, 255) >>> 0x01,0x10,0xff (1, 16, 255) >>> 0b1,0b10000,0b1111111 (1, 16, 127) >>> 0xff,(15*(16**1)+(15*(16**0))) (255, 255) >>> 0x2f,(2*(16**1)+(15*(16**0))) (47, 47) >>> 0xf,0b1111,(1*(2**3)+1*(2**2)+1*(2**1)+1*(2**0)) (15, 15, 15) >>> oct(64),hex(64),bin(64) ('0o100', '0x40', '0b1000000') >>> 0o100,0x40,0b1000000,64 (64, 64, 64, 64)
6 Bitwise Operations
>>> x = 1 #0001 >>> x << 2 #0100 4 >>> x | 2 3 >>> x & 1 1 >>> x = 0b0001 >>> x << 2 4 >>> bin(x << 2) '0b100' >>> bin(x | 0b010) '0b11' >>> bin(x & 0b1) '0b1'
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